The comment in cgroup_file_write is missing some interfaces, such as
'cgroup.threads'. All delegatable files are listed in
'/sys/kernel/cgroup/delegate', so update the comment in cgroup_file_write.
Besides, add a statement that files outside the namespace shouldn't be
visible from inside the delegated namespace.
tj: Reflowed text for consistency.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
For any changes of struct fd representation we need to
turn existing accesses to fields into calls of wrappers.
Accesses to struct fd::flags are very few (3 in linux/file.h,
1 in net/socket.c, 3 in fs/overlayfs/file.c and 3 more in
explicit initializers).
Those can be dealt with in the commit converting to
new layout; accesses to struct fd::file are too many for that.
This commit converts (almost) all of f.file to
fd_file(f). It's not entirely mechanical ('file' is used as
a member name more than just in struct fd) and it does not
even attempt to distinguish the uses in pointer context from
those in boolean context; the latter will be eventually turned
into a separate helper (fd_empty()).
NOTE: mass conversion to fd_empty(), tempting as it
might be, is a bad idea; better do that piecewise in commit
that convert from fdget...() to CLASS(...).
[conflicts in fs/fhandle.c, kernel/bpf/syscall.c, mm/memcontrol.c
caught by git; fs/stat.c one got caught by git grep]
[fs/xattr.c conflict]
Reviewed-by: Christian Brauner <brauner@kernel.org>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
It turns out that the WARN_ON_ONCE() call in css_release_work_fn
introduced by commit ab03125268 ("cgroup: Show # of subsystem CSSes
in cgroup.stat") is incorrect. Although css->nr_descendants must be
0 when a css is released and ready to be freed, the corresponding
cgrp->nr_dying_subsys[ss->id] may not be 0 if a subsystem is activated
and deactivated multiple times with one or more of its previous
activation leaving behind dying csses.
Fix the incorrect warning by removing the cgrp->nr_dying_subsys check.
Fixes: ab03125268 ("cgroup: Show # of subsystem CSSes in cgroup.stat")
Closes: https://lore.kernel.org/cgroups/6f301773-2fce-4602-a391-8af7ef00b2fb@redhat.com/T/#t
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
With the previous commit that eliminates the overlapping partition
root corner cases in the hotplug code, the partition roots passed down
to generate_sched_domains() should not have overlapping CPUs. Enable
overlapping cpuset check for v2 and warn if that happens.
This patch also has the benefit of increasing test coverage of the new
Union-Find cpuset merging code to cgroup v2.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup/for-6.12 is about to receive updates that are dependent on changes
from both for-6.11-fixes and for-6.12. Pull in for-6.11-fixes.
Signed-off-by: Tejun Heo <tj@kernel.org>
It was found that some hotplug operations may cause multiple
rebuild_sched_domains_locked() calls. Some of those intermediate calls
may use cpuset states not in the final correct form leading to incorrect
sched domain setting.
Fix this problem by using the existing force_rebuild flag to inhibit
immediate rebuild_sched_domains_locked() calls if set and only doing
one final call at the end. Also renaming the force_rebuild flag to
force_sd_rebuild to make its meaning for clear.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Commit e2ffe502ba ("cgroup/cpuset: Add cpuset.cpus.exclusive for
v2") adds a user writable cpuset.cpus.exclusive file for setting
exclusive CPUs to be used for the creation of partitions. Since then
effective_xcpus depends on both the cpuset.cpus and cpuset.cpus.exclusive
setting. If cpuset.cpus.exclusive is set, effective_xcpus will depend
only on cpuset.cpus.exclusive. When it is not set, effective_xcpus
will be set according to the cpuset.cpus value when the cpuset becomes
a valid partition root.
When cpuset.cpus is being cleared by the user, effective_xcpus should
only be cleared when cpuset.cpus.exclusive is not set. However, that
is not currently the case.
# cd /sys/fs/cgroup/
# mkdir test
# echo +cpuset > cgroup.subtree_control
# cd test
# echo 3 > cpuset.cpus.exclusive
# cat cpuset.cpus.exclusive.effective
3
# echo > cpuset.cpus
# cat cpuset.cpus.exclusive.effective // was cleared
Fix it by clearing effective_xcpus only if cpuset.cpus.exclusive is
not set.
Fixes: e2ffe502ba ("cgroup/cpuset: Add cpuset.cpus.exclusive for v2")
Cc: stable@vger.kernel.org # v6.7+
Reported-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
According to the implementation of cgroup_css_set_fork(), it will fail
if cset cannot be found and the can_fork/cancel_fork methods will not
be called in this case, which means that the argument 'cset' for these
methods must not be NULL, so remove the unrechable paths in them.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cgroup subsystem state (CSS) is an abstraction in the cgroup layer to
help manage different structures in various cgroup subsystems by being
an embedded element inside a larger structure like cpuset or mem_cgroup.
The /proc/cgroups file shows the number of cgroups for each of the
subsystems. With cgroup v1, the number of CSSes is the same as the
number of cgroups. That is not the case anymore with cgroup v2. The
/proc/cgroups file cannot show the actual number of CSSes for the
subsystems that are bound to cgroup v2.
So if a v2 cgroup subsystem is leaking cgroups (usually memory cgroup),
we can't tell by looking at /proc/cgroups which cgroup subsystems may
be responsible.
As cgroup v2 had deprecated the use of /proc/cgroups, the hierarchical
cgroup.stat file is now being extended to show the number of live and
dying CSSes associated with all the non-inhibited cgroup subsystems that
have been bound to cgroup v2. The number includes CSSes in the current
cgroup as well as in all the descendants underneath it. This will help
us pinpoint which subsystems are responsible for the increasing number
of dying (nr_dying_descendants) cgroups.
The CSSes dying counts are stored in the cgroup structure itself
instead of inside the CSS as suggested by Johannes. This will allow
us to accurately track dying counts of cgroup subsystems that have
recently been disabled in a cgroup. It is now possible that a zero
subsystem number is coupled with a non-zero dying subsystem number.
The cgroup-v2.rst file is updated to discuss this new behavior.
With this patch applied, a sample output from root cgroup.stat file
was shown below.
nr_descendants 56
nr_subsys_cpuset 1
nr_subsys_cpu 43
nr_subsys_io 43
nr_subsys_memory 56
nr_subsys_perf_event 57
nr_subsys_hugetlb 1
nr_subsys_pids 56
nr_subsys_rdma 1
nr_subsys_misc 1
nr_dying_descendants 30
nr_dying_subsys_cpuset 0
nr_dying_subsys_cpu 0
nr_dying_subsys_io 0
nr_dying_subsys_memory 30
nr_dying_subsys_perf_event 0
nr_dying_subsys_hugetlb 0
nr_dying_subsys_pids 0
nr_dying_subsys_rdma 0
nr_dying_subsys_misc 0
Another sample output from system.slice/cgroup.stat was:
nr_descendants 34
nr_subsys_cpuset 0
nr_subsys_cpu 32
nr_subsys_io 32
nr_subsys_memory 34
nr_subsys_perf_event 35
nr_subsys_hugetlb 0
nr_subsys_pids 34
nr_subsys_rdma 0
nr_subsys_misc 0
nr_dying_descendants 30
nr_dying_subsys_cpuset 0
nr_dying_subsys_cpu 0
nr_dying_subsys_io 0
nr_dying_subsys_memory 30
nr_dying_subsys_perf_event 0
nr_dying_subsys_hugetlb 0
nr_dying_subsys_pids 0
nr_dying_subsys_rdma 0
nr_dying_subsys_misc 0
Note that 'debug' controller wasn't used to provide this information because
the controller is not recommended in productions kernels, also many of them
won't enable CONFIG_CGROUP_DEBUG by default.
Similar information could be retrieved with debuggers like drgn but that's
also not always available (e.g. lockdown) and the additional cost of runtime
tracking here is deemed marginal.
tj: Added Michal's paragraphs on why this is not added the debug controller
to the commit message.
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Acked-by: Roman Gushchin <roman.gushchin@linux.dev>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Cc: Michal Koutný <mkoutny@suse.com>
Link: http://lkml.kernel.org/r/20240715150034.2583772-1-longman@redhat.com
Signed-off-by: Tejun Heo <tj@kernel.org>
The process of constructing scheduling domains
involves multiple loops and repeated evaluations, leading to numerous
redundant and ineffective assessments that impact code efficiency.
Here, we use union-find to optimize the merging of cpumasks. By employing
path compression and union by rank, we effectively reduce the number of
lookups and merge comparisons.
Signed-off-by: Xavier <xavier_qy@163.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
There are several functions to decrease attach_in_progress, and they
will wake up cpuset_attach_wq when attach_in_progress is zero. So,
add a helper to make it concise.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Reviewed-by: Kamalesh Babulal <kamalesh.babulal@oracle.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since the SLAB implementation was removed in v6.8, so the
cpuset_slab_spread_rotor is no longer used and can be removed.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently when a process in a group forks and fails due to it's
parent's max restriction, all the cgroups from 'pids_forking' to root
will generate event notifications but only the cgroups from
'pids_over_limit' to root will increase the counter of PIDCG_MAX.
Consider this scenario: there are 4 groups A, B, C,and D, the
relationships are as follows, and user is watching on C.pids.events.
root->A->B->C->D
When a process in D forks and fails due to B.max restriction, the
user will get a spurious event notification because when he wakes up
and reads C.pids.events, he will find that the content has not changed.
To address this issue, only the cgroups from 'pids_over_limit' to root
will have their PIDCG_MAX counters increased and event notifications
generated.
Fixes: 385a635cac ("cgroup/pids: Make event counters hierarchical")
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The child_ecpus_count variable was previously used to update
sibling cpumask when parent's effective_cpus is updated. However, it became
obsolete after commit e2ffe502ba ("cgroup/cpuset: Add
cpuset.cpus.exclusive for v2"). It should be removed.
tj: Restored {} for style consistency.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently the event counting provided by misc.events is hierarchical,
it's not practical if user is only concerned with events of a
specified cgroup. Therefore, introduce misc.events.local collect events
specific to the given cgroup.
This is analogous to memory.events.local and pids.events.local.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In the function cgroup_base_stat_cputime_show, there are five
instances of #ifdef, which makes the code not concise.
To address this, add the function cgroup_force_idle_show
to make the code more succinct.
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The writing of css->cgroup associated with the cgroup root in
rebind_subsystems() is currently protected only by cgroup_mutex.
However, the reading of css->cgroup in both proc_cpuset_show() and
proc_cgroup_show() is protected just by css_set_lock. That makes the
readers susceptible to racing problems like data tearing or caching.
It is also a problem that can be reported by KCSAN.
This can be fixed by using READ_ONCE() and WRITE_ONCE() to access
css->cgroup. Alternatively, the writing of css->cgroup can be moved
under css_set_lock as well which is done by this patch.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Introduce misc.peak to record the historical maximum usage of the
resource, as in some scenarios the value of misc.max could be
adjusted based on the peak usage of the resource.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
An UAF can happen when /proc/cpuset is read as reported in [1].
This can be reproduced by the following methods:
1.add an mdelay(1000) before acquiring the cgroup_lock In the
cgroup_path_ns function.
2.$cat /proc/<pid>/cpuset repeatly.
3.$mount -t cgroup -o cpuset cpuset /sys/fs/cgroup/cpuset/
$umount /sys/fs/cgroup/cpuset/ repeatly.
The race that cause this bug can be shown as below:
(umount) | (cat /proc/<pid>/cpuset)
css_release | proc_cpuset_show
css_release_work_fn | css = task_get_css(tsk, cpuset_cgrp_id);
css_free_rwork_fn | cgroup_path_ns(css->cgroup, ...);
cgroup_destroy_root | mutex_lock(&cgroup_mutex);
rebind_subsystems |
cgroup_free_root |
| // cgrp was freed, UAF
| cgroup_path_ns_locked(cgrp,..);
When the cpuset is initialized, the root node top_cpuset.css.cgrp
will point to &cgrp_dfl_root.cgrp. In cgroup v1, the mount operation will
allocate cgroup_root, and top_cpuset.css.cgrp will point to the allocated
&cgroup_root.cgrp. When the umount operation is executed,
top_cpuset.css.cgrp will be rebound to &cgrp_dfl_root.cgrp.
The problem is that when rebinding to cgrp_dfl_root, there are cases
where the cgroup_root allocated by setting up the root for cgroup v1
is cached. This could lead to a Use-After-Free (UAF) if it is
subsequently freed. The descendant cgroups of cgroup v1 can only be
freed after the css is released. However, the css of the root will never
be released, yet the cgroup_root should be freed when it is unmounted.
This means that obtaining a reference to the css of the root does
not guarantee that css.cgrp->root will not be freed.
Fix this problem by using rcu_read_lock in proc_cpuset_show().
As cgroup_root is kfree_rcu after commit d23b5c5777
("cgroup: Make operations on the cgroup root_list RCU safe"),
css->cgroup won't be freed during the critical section.
To call cgroup_path_ns_locked, css_set_lock is needed, so it is safe to
replace task_get_css with task_css.
[1] https://syzkaller.appspot.com/bug?extid=9b1ff7be974a403aa4cd
Fixes: a79a908fd2 ("cgroup: introduce cgroup namespaces")
Signed-off-by: Chen Ridong <chenridong@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The "cpuset.cpus.exclusive.effective" value is currently limited to a
subset of its "cpuset.cpus". This makes the exclusive CPUs distribution
hierarchy subsumed within the larger "cpuset.cpus" hierarchy. We have to
decide on what CPUs are used locally and what CPUs can be passed down as
exclusive CPUs down the hierarchy and combine them into "cpuset.cpus".
The advantage of the current scheme is to have only one hierarchy to
worry about. However, it make it harder to use as all the "cpuset.cpus"
values have to be properly set along the way down to the designated remote
partition root. It also makes it more cumbersome to find out what CPUs
can be used locally.
Make creation of remote partition simpler by breaking the
dependency of "cpuset.cpus.exclusive" on "cpuset.cpus" and make
them independent entities. Now we have two separate hierarchies -
one for setting "cpuset.cpus.effective" and the other one for setting
"cpuset.cpus.exclusive.effective". We may not need to set "cpuset.cpus"
when we activate a partition root anymore.
Also update Documentation/admin-guide/cgroup-v2.rst and cpuset.c comment
to document this change.
Suggested-by: Petr Malat <oss@malat.biz>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The CS_CPU_EXCLUSIVE flag is currently set whenever cpuset.cpus.exclusive
is set to make sure that the exclusivity test will be run to ensure its
exclusiveness. At the same time, this flag can be changed whenever the
partition root state is changed. For example, the CS_CPU_EXCLUSIVE flag
will be reset whenever a partition root becomes invalid. This makes
using CS_CPU_EXCLUSIVE to ensure exclusiveness a bit fragile.
The current scheme also makes setting up a cpuset.cpus.exclusive
hierarchy to enable remote partition harder as cpuset.cpus.exclusive
cannot overlap with any cpuset.cpus of sibling cpusets if their
cpuset.cpus.exclusive aren't set.
Solve these issues by deferring the setting of CS_CPU_EXCLUSIVE flag
until the cpuset become a valid partition root while adding new checks
in validate_change() to ensure that cpuset.cpus.exclusive of sibling
cpusets cannot overlap.
An additional check is also added to validate_change() to make sure that
cpuset.cpus of one cpuset cannot be a subset of cpuset.cpus.exclusive
of a sibling cpuset to avoid the problem that none of those CPUs will
be available when these exclusive CPUs are extracted out to a newly
enabled partition root. The Documentation/admin-guide/cgroup-v2.rst
file is updated to document the new constraints.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since commit 181c8e091a ("cgroup/cpuset: Introduce remote partition"),
a remote partition can be created underneath a non-partition root cpuset
as long as its exclusive_cpus are set to distribute exclusive CPUs down
to its children. The generate_sched_domains() function, however, doesn't
take into account this new behavior and hence will fail to create the
sched domain needed for a remote root (non-isolated) partition.
There are two issues related to remote partition support. First of
all, generate_sched_domains() has a fast path that is activated if
root_load_balance is true and top_cpuset.nr_subparts is non-zero. The
later condition isn't quite correct for remote partitions as nr_subparts
just shows the number of local child partitions underneath it. There
can be no local child partition under top_cpuset even if there are
remote partitions further down the hierarchy. Fix that by checking
for subpartitions_cpus which contains exclusive CPUs allocated to both
local and remote partitions.
Secondly, the valid partition check for subtree skipping in the csa[]
generation loop isn't enough as remote partition does not need to
have a partition root parent. Fix this problem by breaking csa[] array
generation loop of generate_sched_domains() into v1 and v2 specific parts
and checking a cpuset's exclusive_cpus before skipping its subtree in
the v2 case.
Also simplify generate_sched_domains() for cgroup v2 as only
non-isolating partition roots should be included in building the cpuset
array and none of the v1 scheduling attributes other than a different
way to create an isolated partition are supported.
Fixes: 181c8e091a ("cgroup/cpuset: Introduce remote partition")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
cgroup_exit() needs to do this only if the exiting task is a leader and it
is not the last live thread. The patch doesn't use delay_group_leader(),
atomic_read(signal->live) matches the code css_task_iter_advance() more.
cgroup_release() can now check list_empty(task->cg_list) before it takes
css_set_lock and calls ss_set_skip_task_iters().
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
If only isolated partitions are being created underneath the cgroup root,
there will only be one sched domain with top_cpuset.effective_cpus. We can
skip the unnecessary sched domains scanning code and save some cycles.
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In the cpuset_css_online(), clearing the CS_SCHED_LOAD_BALANCE bit
of cs->flags is guarded by callback_lock and cpuset_mutex. There is
no problem with itself, because it is consistent with the description
of there two global lock at the beginning of this file. However, since
the operation of checking, setting and clearing the flag bit is atomic,
protection of callback_lock is unnecessary here, see CS_SPREAD_*. so
to make it more consistent with the other code, move the operation
outside the critical section of callback_lock.
No functional changes intended.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Even though css_clear_dir would be called to cleanup
all existing cgroup files when css_populate_dir failed,
reclaiming newly created cgroup files before
css_populate_dir returns with failure makes code more
consistent.
Signed-off-by: David Wang <00107082@163.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Hierarchical counting of events is not practical for watching when a
particular pids.max is being hit. Therefore introduce .local flavor of
events file (akin to memory controller) that collects only events
relevant to given cgroup.
The file is only added to the default hierarchy.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The pids.events file should honor the hierarchy, so make the events
propagate from their origin up to the root on the unified hierarchy. The
legacy behavior remains non-hierarchical.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently, when pids.max limit is breached in the hierarchy, the event
is counted and reported in the cgroup where the forking task resides.
This decouples the limit and the notification caused by the limit making
it hard to detect when the actual limit was effected.
Redefine the pids.events:max as: the number of times the limit of the
cgroup was hit.
(Implementation differentiates also "forkfail" event but this is
currently not exposed as it would better fit into pids.stat. It also
differs from pids.events:max only when pids.max is configured on
non-leaf cgroups.)
Since it changes semantics of the original "max" event, introduce this
change only in the v2 API of the controller and add a cgroup2 mount
option to revert to the legacy behavior.
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since commit 51ffe41178 ("cpuset: convert away from cftype->read()"),
cpuset_common_file_read() has been renamed.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The struct cpuset is kzalloc'd, all the members are zeroed already,
so don't need nodes_clear() here.
No functional changes intended.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Change relax_domain_level checks so that it would be possible
to include or exclude all domains from newidle balancing.
This matches the behavior described in the documentation:
-1 no request. use system default or follow request of others.
0 no search.
1 search siblings (hyperthreads in a core).
"2" enables levels 0 and 1, level_max excludes the last (level_max)
level, and level_max+1 includes all levels.
Fixes: 1d3504fcf5 ("sched, cpuset: customize sched domains, core")
Signed-off-by: Vitalii Bursov <vitaly@bursov.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Tested-by: Dietmar Eggemann <dietmar.eggemann@arm.com>
Reviewed-by: Vincent Guittot <vincent.guittot@linaro.org>
Reviewed-by: Valentin Schneider <vschneid@redhat.com>
Link: https://lore.kernel.org/r/bd6de28e80073c79466ec6401cdeae78f0d4423d.1714488502.git.vitaly@bursov.com
This closely resembles helpers added for the global cgroup_rstat_lock in
commit fc29e04ae1 ("cgroup/rstat: add cgroup_rstat_lock helpers and
tracepoints"). This is for the per CPU lock cgroup_rstat_cpu_lock.
Based on production workloads, we observe the fast-path "update" function
cgroup_rstat_updated() is invoked around 3 million times per sec, while the
"flush" function cgroup_rstat_flush_locked(), walking each possible CPU,
can see periodic spikes of 700 invocations/sec.
For this reason, the tracepoints are split into normal and fastpath
versions for this per-CPU lock. Making it feasible for production to
continuously monitor the non-fastpath tracepoint to detect lock contention
issues. The reason for monitoring is that lock disables IRQs which can
disturb e.g. softirq processing on the local CPUs involved. When the
global cgroup_rstat_lock stops disabling IRQs (e.g converted to a mutex),
this per CPU lock becomes the next bottleneck that can introduce latency
variations.
A practical bpftrace script for monitoring contention latency:
bpftrace -e '
tracepoint:cgroup:cgroup_rstat_cpu_lock_contended {
@start[tid]=nsecs; @cnt[probe]=count()}
tracepoint:cgroup:cgroup_rstat_cpu_locked {
if (args->contended) {
@wait_ns=hist(nsecs-@start[tid]); delete(@start[tid]);}
@cnt[probe]=count()}
interval:s:1 {time("%H:%M:%S "); print(@wait_ns); print(@cnt); clear(@cnt);}'
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
The comment here is outdated and can cause confusion, from the code
perspective, there’s also no need for new comment, so just remove it.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Acked-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Commit 8996f93fc3 ("cgroup/cpuset: Statically initialize more
members of top_cpuset") uses an incorrect "<" relational operator for
the CS_SCHED_LOAD_BALANCE bit when initializing the top_cpuset. This
results in load_balancing turned off by default in the top cpuset which
is bad for performance.
Fix this by using the BIT() helper macro to set the desired top_cpuset
flags and avoid similar mistake from being made in the future.
Fixes: 8996f93fc3 ("cgroup/cpuset: Statically initialize more members of top_cpuset")
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
In cpuset_css_online(), CS_SCHED_LOAD_BALANCE will be cleared twice,
the former one in the is_in_v2_mode() case could be removed because
is_in_v2_mode() can be true for cgroup v1 if the "cpuset_v2_mode"
mount option is specified, that balance flag change isn't appropriate
for this particular case.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Initializing top_cpuset.relax_domain_level and setting
CS_SCHED_LOAD_BALANCE to top_cpuset.flags in cpuset_init() could be
completed at the time of top_cpuset definition by compiler.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Reviewed-by: Waiman Long <longman@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
No need to continue the for_each_subsys loop after the token matches the
name of subsys and cgroup_no_v1_mask is set.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Currently cgroup1_pidlist_destroy_all() will be called when releasing
cgroup even if the cgroup is on default hierarchy, however it doesn't
make any sense for v2 to destroy pidlist of v1.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
The freezer->lock was replaced by freezer_mutex in commit e5ced8ebb1
("cgroup_freezer: replace freezer->lock with freezer_mutex"), so the
comment here is out-of-date, update it.
Signed-off-by: Xiu Jianfeng <xiujianfeng@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Recent change to cgroup_rstat_flush_release added a
parameter cgrp, which is used by tracepoint to correlate
with other tracepoints that also have this cgrp.
The kernel test robot detected kernel doc was missing
a description of this member.
Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202404170821.HwZGISTY-lkp@intel.com/
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
This commit enhances the ability to troubleshoot the global
cgroup_rstat_lock by introducing wrapper helper functions for the lock
along with associated tracepoints.
Although global, the cgroup_rstat_lock helper APIs and tracepoints take
arguments such as cgroup pointer and cpu_in_loop variable. This
adjustment is made because flushing occurs per cgroup despite the lock
being global. Hence, when troubleshooting, it's important to identify the
relevant cgroup. The cpu_in_loop variable is necessary because the global
lock may be released within the main flushing loop that traverses CPUs.
In the tracepoints, the cpu_in_loop value is set to -1 when acquiring the
main lock; otherwise, it denotes the CPU number processed last.
The new feature in this patchset is detecting when lock is contended. The
tracepoints are implemented with production in mind. For minimum overhead
attach to cgroup:cgroup_rstat_lock_contended, which only gets activated
when trylock detects lock is contended. A quick production check for
issues could be done via this perf commands:
perf record -g -e cgroup:cgroup_rstat_lock_contended
Next natural question would be asking how long time do lock contenders
wait for obtaining the lock. This can be answered by measuring the time
between cgroup:cgroup_rstat_lock_contended and cgroup:cgroup_rstat_locked
when args->contended is set. Like this bpftrace script:
bpftrace -e '
tracepoint:cgroup:cgroup_rstat_lock_contended {@start[tid]=nsecs}
tracepoint:cgroup:cgroup_rstat_locked {
if (args->contended) {
@wait_ns=hist(nsecs-@start[tid]); delete(@start[tid]);}}
interval:s:1 {time("%H:%M:%S "); print(@wait_ns); }'
Extending with time spend holding the lock will be more expensive as this
also looks at all the non-contended cases.
Like this bpftrace script:
bpftrace -e '
tracepoint:cgroup:cgroup_rstat_lock_contended {@start[tid]=nsecs}
tracepoint:cgroup:cgroup_rstat_locked { @locked[tid]=nsecs;
if (args->contended) {
@wait_ns=hist(nsecs-@start[tid]); delete(@start[tid]);}}
tracepoint:cgroup:cgroup_rstat_unlock {
@locked_ns=hist(nsecs-@locked[tid]); delete(@locked[tid]);}
interval:s:1 {time("%H:%M:%S "); print(@wait_ns);print(@locked_ns); }'
Signed-off-by: Jesper Dangaard Brouer <hawk@kernel.org>
Signed-off-by: Tejun Heo <tj@kernel.org>
Atomic counters are in kzalloc'd struct. They are zeroed already and
atomic64_t does not need special initialization
(cf kernel/trace/trace_clock.c:trace_counter).
Signed-off-by: Michal Koutný <mkoutny@suse.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Since commit 3a5a6d0c2b03("cpuset: don't nest cgroup_mutex inside
get_online_cpus()"), cpuset hotplug was done asynchronously via a work
function. This is to avoid recursive locking of cgroup_mutex.
Since then, the cgroup locking scheme has changed quite a bit. A
cpuset_mutex was introduced to protect cpuset specific operations.
The cpuset_mutex is then replaced by a cpuset_rwsem. With commit
d74b27d63a ("cgroup/cpuset: Change cpuset_rwsem and hotplug lock
order"), cpu_hotplug_lock is acquired before cpuset_rwsem. Later on,
cpuset_rwsem is reverted back to cpuset_mutex. All these locking changes
allow the hotplug code to call into cpuset core directly.
The following commits were also merged due to the asynchronous nature
of cpuset hotplug processing.
- commit b22afcdf04 ("cpu/hotplug: Cure the cpusets trainwreck")
- commit 50e7663233 ("sched/cpuset/pm: Fix cpuset vs. suspend-resume
bugs")
- commit 28b89b9e6f ("cpuset: handle race between CPU hotplug and
cpuset_hotplug_work")
Clean up all these bandages by making cpuset hotplug
processing synchronous again with the exception that the call to
cgroup_transfer_tasks() to transfer tasks out of an empty cgroup v1
cpuset, if necessary, will still be done via a work function due to the
existing cgroup_mutex -> cpu_hotplug_lock dependency. It is possible
to reverse that dependency, but that will require updating a number of
different cgroup controllers. This special hotplug code path should be
rarely taken anyway.
As all the cpuset states will be updated by the end of the hotplug
operation, we can revert most the above commits except commit
50e7663233 ("sched/cpuset/pm: Fix cpuset vs. suspend-resume bugs")
which is partially reverted. Also removing some cpus_read_lock trylock
attempts in the cpuset partition code as they are no longer necessary
since the cpu_hotplug_lock is now held for the whole duration of the
cpuset hotplug code path.
Signed-off-by: Waiman Long <longman@redhat.com>
Tested-by: Valentin Schneider <vschneid@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Pull networking updates from Jakub Kicinski:
"Core & protocols:
- Large effort by Eric to lower rtnl_lock pressure and remove locks:
- Make commonly used parts of rtnetlink (address, route dumps
etc) lockless, protected by RCU instead of rtnl_lock.
- Add a netns exit callback which already holds rtnl_lock,
allowing netns exit to take rtnl_lock once in the core instead
of once for each driver / callback.
- Remove locks / serialization in the socket diag interface.
- Remove 6 calls to synchronize_rcu() while holding rtnl_lock.
- Remove the dev_base_lock, depend on RCU where necessary.
- Support busy polling on a per-epoll context basis. Poll length and
budget parameters can be set independently of system defaults.
- Introduce struct net_hotdata, to make sure read-mostly global
config variables fit in as few cache lines as possible.
- Add optional per-nexthop statistics to ease monitoring / debug of
ECMP imbalance problems.
- Support TCP_NOTSENT_LOWAT in MPTCP.
- Ensure that IPv6 temporary addresses' preferred lifetimes are long
enough, compared to other configured lifetimes, and at least 2 sec.
- Support forwarding of ICMP Error messages in IPSec, per RFC 4301.
- Add support for the independent control state machine for bonding
per IEEE 802.1AX-2008 5.4.15 in addition to the existing coupled
control state machine.
- Add "network ID" to MCTP socket APIs to support hosts with multiple
disjoint MCTP networks.
- Re-use the mono_delivery_time skbuff bit for packets which user
space wants to be sent at a specified time. Maintain the timing
information while traversing veth links, bridge etc.
- Take advantage of MSG_SPLICE_PAGES for RxRPC DATA and ACK packets.
- Simplify many places iterating over netdevs by using an xarray
instead of a hash table walk (hash table remains in place, for use
on fastpaths).
- Speed up scanning for expired routes by keeping a dedicated list.
- Speed up "generic" XDP by trying harder to avoid large allocations.
- Support attaching arbitrary metadata to netconsole messages.
Things we sprinkled into general kernel code:
- Enforce VM_IOREMAP flag and range in ioremap_page_range and
introduce VM_SPARSE kind and vm_area_[un]map_pages (used by
bpf_arena).
- Rework selftest harness to enable the use of the full range of ksft
exit code (pass, fail, skip, xfail, xpass).
Netfilter:
- Allow userspace to define a table that is exclusively owned by a
daemon (via netlink socket aliveness) without auto-removing this
table when the userspace program exits. Such table gets marked as
orphaned and a restarting management daemon can re-attach/regain
ownership.
- Speed up element insertions to nftables' concatenated-ranges set
type. Compact a few related data structures.
BPF:
- Add BPF token support for delegating a subset of BPF subsystem
functionality from privileged system-wide daemons such as systemd
through special mount options for userns-bound BPF fs to a trusted
& unprivileged application.
- Introduce bpf_arena which is sparse shared memory region between
BPF program and user space where structures inside the arena can
have pointers to other areas of the arena, and pointers work
seamlessly for both user-space programs and BPF programs.
- Introduce may_goto instruction that is a contract between the
verifier and the program. The verifier allows the program to loop
assuming it's behaving well, but reserves the right to terminate
it.
- Extend the BPF verifier to enable static subprog calls in spin lock
critical sections.
- Support registration of struct_ops types from modules which helps
projects like fuse-bpf that seeks to implement a new struct_ops
type.
- Add support for retrieval of cookies for perf/kprobe multi links.
- Support arbitrary TCP SYN cookie generation / validation in the TC
layer with BPF to allow creating SYN flood handling in BPF
firewalls.
- Add code generation to inline the bpf_kptr_xchg() helper which
improves performance when stashing/popping the allocated BPF
objects.
Wireless:
- Add SPP (signaling and payload protected) AMSDU support.
- Support wider bandwidth OFDMA, as required for EHT operation.
Driver API:
- Major overhaul of the Energy Efficient Ethernet internals to
support new link modes (2.5GE, 5GE), share more code between
drivers (especially those using phylib), and encourage more
uniform behavior. Convert and clean up drivers.
- Define an API for querying per netdev queue statistics from
drivers.
- IPSec: account in global stats for fully offloaded sessions.
- Create a concept of Ethernet PHY Packages at the Device Tree level,
to allow parameterizing the existing PHY package code.
- Enable Rx hashing (RSS) on GTP protocol fields.
Misc:
- Improvements and refactoring all over networking selftests.
- Create uniform module aliases for TC classifiers, actions, and
packet schedulers to simplify creating modprobe policies.
- Address all missing MODULE_DESCRIPTION() warnings in networking.
- Extend the Netlink descriptions in YAML to cover message
encapsulation or "Netlink polymorphism", where interpretation of
nested attributes depends on link type, classifier type or some
other "class type".
Drivers:
- Ethernet high-speed NICs:
- Add a new driver for Marvell's Octeon PCI Endpoint NIC VF.
- Intel (100G, ice, idpf):
- support E825-C devices
- nVidia/Mellanox:
- support devices with one port and multiple PCIe links
- Broadcom (bnxt):
- support n-tuple filters
- support configuring the RSS key
- Wangxun (ngbe/txgbe):
- implement irq_domain for TXGBE's sub-interrupts
- Pensando/AMD:
- support XDP
- optimize queue submission and wakeup handling (+17% bps)
- optimize struct layout, saving 28% of memory on queues
- Ethernet NICs embedded and virtual:
- Google cloud vNIC:
- refactor driver to perform memory allocations for new queue
config before stopping and freeing the old queue memory
- Synopsys (stmmac):
- obey queueMaxSDU and implement counters required by 802.1Qbv
- Renesas (ravb):
- support packet checksum offload
- suspend to RAM and runtime PM support
- Ethernet switches:
- nVidia/Mellanox:
- support for nexthop group statistics
- Microchip:
- ksz8: implement PHY loopback
- add support for KSZ8567, a 7-port 10/100Mbps switch
- PTP:
- New driver for RENESAS FemtoClock3 Wireless clock generator.
- Support OCP PTP cards designed and built by Adva.
- CAN:
- Support recvmsg() flags for own, local and remote traffic on CAN
BCM sockets.
- Support for esd GmbH PCIe/402 CAN device family.
- m_can:
- Rx/Tx submission coalescing
- wake on frame Rx
- WiFi:
- Intel (iwlwifi):
- enable signaling and payload protected A-MSDUs
- support wider-bandwidth OFDMA
- support for new devices
- bump FW API to 89 for AX devices; 90 for BZ/SC devices
- MediaTek (mt76):
- mt7915: newer ADIE version support
- mt7925: radio temperature sensor support
- Qualcomm (ath11k):
- support 6 GHz station power modes: Low Power Indoor (LPI),
Standard Power) SP and Very Low Power (VLP)
- QCA6390 & WCN6855: support 2 concurrent station interfaces
- QCA2066 support
- Qualcomm (ath12k):
- refactoring in preparation for Multi-Link Operation (MLO)
support
- 1024 Block Ack window size support
- firmware-2.bin support
- support having multiple identical PCI devices (firmware needs
to have ATH12K_FW_FEATURE_MULTI_QRTR_ID)
- QCN9274: support split-PHY devices
- WCN7850: enable Power Save Mode in station mode
- WCN7850: P2P support
- RealTek:
- rtw88: support for more rtw8811cu and rtw8821cu devices
- rtw89: support SCAN_RANDOM_SN and SET_SCAN_DWELL
- rtlwifi: speed up USB firmware initialization
- rtwl8xxxu:
- RTL8188F: concurrent interface support
- Channel Switch Announcement (CSA) support in AP mode
- Broadcom (brcmfmac):
- per-vendor feature support
- per-vendor SAE password setup
- DMI nvram filename quirk for ACEPC W5 Pro"
* tag 'net-next-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (2255 commits)
nexthop: Fix splat with CONFIG_DEBUG_PREEMPT=y
nexthop: Fix out-of-bounds access during attribute validation
nexthop: Only parse NHA_OP_FLAGS for dump messages that require it
nexthop: Only parse NHA_OP_FLAGS for get messages that require it
bpf: move sleepable flag from bpf_prog_aux to bpf_prog
bpf: hardcode BPF_PROG_PACK_SIZE to 2MB * num_possible_nodes()
selftests/bpf: Add kprobe multi triggering benchmarks
ptp: Move from simple ida to xarray
vxlan: Remove generic .ndo_get_stats64
vxlan: Do not alloc tstats manually
devlink: Add comments to use netlink gen tool
nfp: flower: handle acti_netdevs allocation failure
net/packet: Add getsockopt support for PACKET_COPY_THRESH
net/netlink: Add getsockopt support for NETLINK_LISTEN_ALL_NSID
selftests/bpf: Add bpf_arena_htab test.
selftests/bpf: Add bpf_arena_list test.
selftests/bpf: Add unit tests for bpf_arena_alloc/free_pages
bpf: Add helper macro bpf_addr_space_cast()
libbpf: Recognize __arena global variables.
bpftool: Recognize arena map type
...
Pull cgroup updates from Tejun Heo:
"A quiet cycle. One trivial doc update patch. Two patches to drop the
now defunct memory_spread_slab feature from cgroup1 cpuset"
* tag 'cgroup-for-6.9' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cgroup/cpuset: Mark memory_spread_slab as obsolete
cgroup/cpuset: Remove cpuset_do_slab_mem_spread()
docs: cgroup-v1: add missing code-block tags
