- Replace NAPI_SKB_CACHE_HALF with NAPI_SKB_CACHE_FREE
- Only free 32 skbs in napi_skb_cache_put()
Since the first patch adjusting NAPI_SKB_CACHE_SIZE to 128, the number
of packets to be freed in the softirq was increased from 32 to 64.
Considering a subsequent net_rx_action() calling napi_poll() a few
times can easily consume the 64 available slots and we can afford
keeping a higher value of sk_buffs in per-cpu storage, decrease
NAPI_SKB_CACHE_FREE to 32 like before. So now the logic is 1) keeping
96 skbs, 2) freeing 32 skbs at one time.
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://patch.msgid.link/20251118070646.61344-4-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
After commit b61785852e ("net: increase skb_defer_max default to 128")
changed the value sysctl_skb_defer_max to avoid many calls to
kick_defer_list_purge(), the same situation can be applied to
NAPI_SKB_CACHE_SIZE that was proposed in 2016. It's a trade-off between
using pre-allocated memory in skb_cache and saving more a bit heavy
function calls in the softirq context.
With this patch applied, we can have more skbs per-cpu to accelerate the
sending path that needs to acquire new skbs.
Suggested-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://patch.msgid.link/20251118070646.61344-2-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This is a followup of commit e20dfbad8a ("net: fix napi_consume_skb()
with alien skbs").
Now the per-cpu napi_skb_cache is populated from TX completion path,
we can make use of this cache, especially for cpus not used
from a driver NAPI poll (primary user of napi_cache).
We can use the napi_skb_cache only if current context is not from hard irq.
With this patch, I consistently reach 130 Mpps on my UDP tx stress test
and reduce SLUB spinlock contention to smaller values.
Note there is still some SLUB contention for skb->head allocations.
I had to tune /sys/kernel/slab/skbuff_small_head/cpu_partial
and /sys/kernel/slab/skbuff_small_head/min_partial depending
on the platform taxonomy.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jason Xing <kerneljasonxing@gmail.com>
Tested-by: Jason Xing <kerneljasonxing@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20251116202717.1542829-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Following loop in napi_skb_cache_put() is unrolled by the compiler
even if CONFIG_KASAN is not enabled:
for (i = NAPI_SKB_CACHE_HALF; i < NAPI_SKB_CACHE_SIZE; i++)
kasan_mempool_unpoison_object(nc->skb_cache[i],
kmem_cache_size(net_hotdata.skbuff_cache));
We have 32 times this sequence, for a total of 384 bytes.
48 8b 3d 00 00 00 00 net_hotdata.skbuff_cache,%rdi
e8 00 00 00 00 call kmem_cache_size
This is because kmem_cache_size() is not an inline and not const,
and kasan_unpoison_object_data() is an inline function.
Cache kmem_cache_size() result in a variable, so that
the compiler can remove dead code (and variable) when/if
CONFIG_KASAN is unset.
After this patch, napi_skb_cache_put() is inlined in its callers,
and we avoid one kmem_cache_size() call in napi_skb_cache_get()
and napi_skb_cache_get_bulk().
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Link: https://patch.msgid.link/20251016182911.1132792-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Provide a PSP implementation for netdevsim.
Use psp_dev_encapsulate() and psp_dev_rcv() to do actual encapsulation
and decapsulation on skbs, but perform no encryption or decryption. In
order to make encryption with a bad key result in a drop on the peer's
rx side, we stash our psd's generation number in the first byte of each
key before handing to the peer.
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Co-developed-by: Daniel Zahka <daniel.zahka@gmail.com>
Signed-off-by: Daniel Zahka <daniel.zahka@gmail.com>
Link: https://patch.msgid.link/20250927225420.1443468-2-kuba@kernel.org
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Currently, alloc_skb_with_frags() will only fill (MAX_SKB_FRAGS - 1)
slots. I think it should use all MAX_SKB_FRAGS slots, as callers of
alloc_skb_with_frags() will size their allocation of frags based
on MAX_SKB_FRAGS.
This issue was discovered via a test patch that sets 'order' to 0
in alloc_skb_with_frags(), which effectively tests/simulates high
fragmentation. In this case sendmsg() on unix sockets will fail every
time for large allocations. If the PAGE_SIZE is 4K, then data_len will
request 68K or 17 pages, but alloc_skb_with_frags() can only allocate
64K in this case or 16 pages.
Fixes: 09c2c90705 ("net: allow alloc_skb_with_frags() to allocate bigger packets")
Signed-off-by: Jason Baron <jbaron@akamai.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20250922191957.2855612-1-jbaron@akamai.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
If *len is equal to 0 at the beginning of __splice_segment
it returns true directly. But when decreasing *len from
a positive number to 0 in __splice_segment, it returns false.
The __skb_splice_bits needs to call __splice_segment again.
Recheck *len if it changes, return true in time.
Reduce unnecessary calls to __splice_segment.
Signed-off-by: Pengtao He <hept.hept.hept@gmail.com>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250819021551.8361-1-hept.hept.hept@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Since its introduction in commit 6fa01ccd88 ("skbuff: Add pskb_extract()
helper function"), pskb_carve_frag_list() never used the argument @skb.
Drop it and adapt the only caller.
No functional change intended.
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Since its introduction in commit ce098da149 ("skbuff: Introduce
slab_build_skb()"), __slab_build_skb() never used the @skb argument. Remove
it and adapt both callers.
No functional change intended.
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: Michal Luczaj <mhal@rbox.co>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
skb_ensure_writable should succeed when it's trying to write to the
header of the unreadable skbs, so it doesn't need an unconditional
skb_frags_readable check. The preceding pskb_may_pull() call will
succeed if write_len is within the head and fail if we're trying to
write to the unreadable payload, so we don't need an additional check.
Removing this check restores DSCP functionality with unreadable skbs as
it's called from dscp_tg.
Cc: willemb@google.com
Cc: asml.silence@gmail.com
Fixes: 65249feb6b ("net: add support for skbs with unreadable frags")
Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250615200733.520113-1-almasrymina@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Now that the only remaining caller of __skb_checksum() is
skb_checksum(), fold __skb_checksum() into skb_checksum(). This makes
struct skb_checksum_ops unnecessary, so remove that too and simply do
the "regular" net checksum. It also makes the wrapper functions
csum_partial_ext() and csum_block_add_ext() unnecessary, so remove those
too and just use the underlying functions.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://patch.msgid.link/20250519175012.36581-7-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Add skb_crc32c(), which calculates the CRC32C of a sk_buff. It will
replace __skb_checksum(), which unnecessarily supports arbitrary
checksums. Compared to __skb_checksum(), skb_crc32c():
- Uses the correct type for CRC32C values (u32, not __wsum).
- Does not require the caller to provide a skb_checksum_ops struct.
- Is faster because it does not use indirect calls and does not use
the very slow crc32c_combine().
According to commit 2817a336d4 ("net: skb_checksum: allow custom
update/combine for walking skb") which added __skb_checksum(), the
original motivation for the abstraction layer was to avoid code
duplication for CRC32C and other checksums in the future. However:
- No additional checksums showed up after CRC32C. __skb_checksum()
is only used with the "regular" net checksum and CRC32C.
- Indirect calls are expensive. Commit 2544af0344 ("net: avoid
indirect calls in L4 checksum calculation") worked around this
using the INDIRECT_CALL_1 macro. But that only avoided the indirect
call for the net checksum, and at the cost of an extra branch.
- The checksums use different types (__wsum and u32), causing casts
to be needed.
- It made the checksums of fragments be combined (rather than
chained) for both checksums, despite this being highly
counterproductive for CRC32C due to how slow crc32c_combine() is.
This can clearly be seen in commit 4c2f245496 ("sctp: linearize
early if it's not GSO") which tried to work around this performance
bug. With a dedicated function for each checksum, we can instead
just use the proper strategy for each checksum.
As shown by the following tables, the new function skb_crc32c() is
faster than __skb_checksum(), with the improvement varying greatly from
5% to 2500% depending on the case. The largest improvements come from
fragmented packets, mainly due to eliminating the inefficient
crc32c_combine(). But linear packets are improved too, especially
shorter ones, mainly due to eliminating indirect calls. These
benchmarks were done on AMD Zen 5. On that CPU, Linux uses IBRS instead
of retpoline; an even greater improvement might be seen with retpoline:
Linear sk_buffs
Length in bytes __skb_checksum cycles skb_crc32c cycles
=============== ===================== =================
64 43 18
256 94 77
1420 204 161
16384 1735 1642
Nonlinear sk_buffs (even split between head and one fragment)
Length in bytes __skb_checksum cycles skb_crc32c cycles
=============== ===================== =================
64 579 22
256 829 77
1420 1506 194
16384 4365 1682
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Hannes Reinecke <hare@suse.de>
Link: https://patch.msgid.link/20250519175012.36581-3-ebiggers@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Augment dmabuf binding to be able to handle TX. Additional to all the RX
binding, we also create tx_vec needed for the TX path.
Provide API for sendmsg to be able to send dmabufs bound to this device:
- Provide a new dmabuf_tx_cmsg which includes the dmabuf to send from.
- MSG_ZEROCOPY with SCM_DEVMEM_DMABUF cmsg indicates send from dma-buf.
Devmem is uncopyable, so piggyback off the existing MSG_ZEROCOPY
implementation, while disabling instances where MSG_ZEROCOPY falls back
to copying.
We additionally pipe the binding down to the new
zerocopy_fill_skb_from_devmem which fills a TX skb with net_iov netmems
instead of the traditional page netmems.
We also special case skb_frag_dma_map to return the dma-address of these
dmabuf net_iovs instead of attempting to map pages.
The TX path may release the dmabuf in a context where we cannot wait.
This happens when the user unbinds a TX dmabuf while there are still
references to its netmems in the TX path. In that case, the netmems will
be put_netmem'd from a context where we can't unmap the dmabuf, Resolve
this by making __net_devmem_dmabuf_binding_free schedule_work'd.
Based on work by Stanislav Fomichev <sdf@fomichev.me>. A lot of the meat
of the implementation came from devmem TCP RFC v1[1], which included the
TX path, but Stan did all the rebasing on top of netmem/net_iov.
Cc: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Kaiyuan Zhang <kaiyuanz@google.com>
Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-5-almasrymina@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Currently net_iovs support only pp ref counts, and do not support a
page ref equivalent.
This is fine for the RX path as net_iovs are used exclusively with the
pp and only pp refcounting is needed there. The TX path however does not
use pp ref counts, thus, support for get_page/put_page equivalent is
needed for netmem.
Support get_netmem/put_netmem. Check the type of the netmem before
passing it to page or net_iov specific code to obtain a page ref
equivalent.
For dmabuf net_iovs, we obtain a ref on the underlying binding. This
ensures the entire binding doesn't disappear until all the net_iovs have
been put_netmem'ed. We do not need to track the refcount of individual
dmabuf net_iovs as we don't allocate/free them from a pool similar to
what the buddy allocator does for pages.
This code is written to be extensible by other net_iov implementers.
get_netmem/put_netmem will check the type of the netmem and route it to
the correct helper:
pages -> [get|put]_page()
dmabuf net_iovs -> net_devmem_[get|put]_net_iov()
new net_iovs -> new helpers
Signed-off-by: Mina Almasry <almasrymina@google.com>
Acked-by: Stanislav Fomichev <sdf@fomichev.me>
Link: https://patch.msgid.link/20250508004830.4100853-3-almasrymina@google.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Add SOF_TIMESTAMPING_TX_COMPLETION, for requesting a software timestamp
when hardware reports a packet completed.
Completion tstamp is useful for Bluetooth, as hardware timestamps do not
exist in the HCI specification except for ISO packets, and the hardware
has a queue where packets may wait. In this case the software SND
timestamp only reflects the kernel-side part of the total latency
(usually small) and queue length (usually 0 unless HW buffers
congested), whereas the completion report time is more informative of
the true latency.
It may also be useful in other cases where HW TX timestamps cannot be
obtained and user wants to estimate an upper bound to when the TX
probably happened.
Signed-off-by: Pauli Virtanen <pav@iki.fi>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Signed-off-by: Luiz Augusto von Dentz <luiz.von.dentz@intel.com>
Add a function to get an array of skbs from the NAPI percpu cache.
It's supposed to be a drop-in replacement for
kmem_cache_alloc_bulk(skbuff_head_cache, GFP_ATOMIC) and
xdp_alloc_skb_bulk(GFP_ATOMIC). The difference (apart from the
requirement to call it only from the BH) is that it tries to use
as many NAPI cache entries for skbs as possible, and allocate new
ones only if needed.
The logic is as follows:
* there is enough skbs in the cache: decache them and return to the
caller;
* not enough: try refilling the cache first. If there is now enough
skbs, return;
* still not enough: try allocating skbs directly to the output array
with %GFP_ZERO, maybe we'll be able to get some. If there's now
enough, return;
* still not enough: return as many as we were able to obtain.
Most of times, if called from the NAPI polling loop, the first one will
be true, sometimes (rarely) the second one. The third and the fourth --
only under heavy memory pressure.
It can save significant amounts of CPU cycles if there are GRO cycles
and/or Tx completion cycles (anything that descends to
napi_skb_cache_put()) happening on this CPU.
Tested-by: Daniel Xu <dxu@dxuuu.xyz>
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
We found an issue when using bpf_redirect with ipvs NAT mode after
commit ff70202b2d ("dev_forward_skb: do not scrub skb mark within
the same name space"). Particularly, we use bpf_redirect to return
the skb directly back to the netif it comes from, i.e., xnet is
false in skb_scrub_packet(), and then ipvs_property is preserved
and SNAT is skipped in the rx path.
ipvs_property has been already cleared when netns is changed in
commit 2b5ec1a5f9 ("netfilter/ipvs: clear ipvs_property flag when
SKB net namespace changed"). This patch just clears it in spite of
netns.
Fixes: 2b5ec1a5f9 ("netfilter/ipvs: clear ipvs_property flag when SKB net namespace changed")
Signed-off-by: Philo Lu <lulie@linux.alibaba.com>
Acked-by: Julian Anastasov <ja@ssi.bg>
Link: https://patch.msgid.link/20250222033518.126087-1-lulie@linux.alibaba.com
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Martin KaFai Lau says:
====================
pull-request: bpf-next 2025-02-20
We've added 19 non-merge commits during the last 8 day(s) which contain
a total of 35 files changed, 1126 insertions(+), 53 deletions(-).
The main changes are:
1) Add TCP_RTO_MAX_MS support to bpf_set/getsockopt, from Jason Xing
2) Add network TX timestamping support to BPF sock_ops, from Jason Xing
3) Add TX metadata Launch Time support, from Song Yoong Siang
* tag 'for-netdev' of https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next:
igc: Add launch time support to XDP ZC
igc: Refactor empty frame insertion for launch time support
net: stmmac: Add launch time support to XDP ZC
selftests/bpf: Add launch time request to xdp_hw_metadata
xsk: Add launch time hardware offload support to XDP Tx metadata
selftests/bpf: Add simple bpf tests in the tx path for timestamping feature
bpf: Support selective sampling for bpf timestamping
bpf: Add BPF_SOCK_OPS_TSTAMP_SENDMSG_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_ACK_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_SND_HW_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_SND_SW_CB callback
bpf: Add BPF_SOCK_OPS_TSTAMP_SCHED_CB callback
net-timestamp: Prepare for isolating two modes of SO_TIMESTAMPING
bpf: Disable unsafe helpers in TX timestamping callbacks
bpf: Prevent unsafe access to the sock fields in the BPF timestamping callback
bpf: Prepare the sock_ops ctx and call bpf prog for TX timestamping
bpf: Add networking timestamping support to bpf_get/setsockopt()
selftests/bpf: Add rto max for bpf_setsockopt test
bpf: Support TCP_RTO_MAX_MS for bpf_setsockopt
====================
Link: https://patch.msgid.link/20250221022104.386462-1-martin.lau@linux.dev
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Support the ACK case for bpf timestamping.
Add a new sock_ops callback, BPF_SOCK_OPS_TSTAMP_ACK_CB. This
callback will occur at the same timestamping point as the user
space's SCM_TSTAMP_ACK. The BPF program can use it to get the
same SCM_TSTAMP_ACK timestamp without modifying the user-space
application.
This patch extends txstamp_ack to two bits: 1 stands for
SO_TIMESTAMPING mode, 2 bpf extension.
Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-10-kerneljasonxing@gmail.com
Support hw SCM_TSTAMP_SND case for bpf timestamping.
Add a new sock_ops callback, BPF_SOCK_OPS_TSTAMP_SND_HW_CB. This
callback will occur at the same timestamping point as the user
space's hardware SCM_TSTAMP_SND. The BPF program can use it to
get the same SCM_TSTAMP_SND timestamp without modifying the
user-space application.
To avoid increasing the code complexity, replace SKBTX_HW_TSTAMP
with SKBTX_HW_TSTAMP_NOBPF instead of changing numerous callers
from driver side using SKBTX_HW_TSTAMP. The new definition of
SKBTX_HW_TSTAMP means the combination tests of socket timestamping
and bpf timestamping. After this patch, drivers can work under the
bpf timestamping.
Considering some drivers don't assign the skb with hardware
timestamp, this patch does the assignment and then BPF program
can acquire the hwstamp from skb directly.
Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-9-kerneljasonxing@gmail.com
Support sw SCM_TSTAMP_SND case for bpf timestamping.
Add a new sock_ops callback, BPF_SOCK_OPS_TSTAMP_SND_SW_CB. This
callback will occur at the same timestamping point as the user
space's software SCM_TSTAMP_SND. The BPF program can use it to
get the same SCM_TSTAMP_SND timestamp without modifying the
user-space application.
Based on this patch, BPF program will get the software
timestamp when the driver is ready to send the skb. In the
sebsequent patch, the hardware timestamp will be supported.
Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-8-kerneljasonxing@gmail.com
Support SCM_TSTAMP_SCHED case for bpf timestamping.
Add a new sock_ops callback, BPF_SOCK_OPS_TSTAMP_SCHED_CB. This
callback will occur at the same timestamping point as the user
space's SCM_TSTAMP_SCHED. The BPF program can use it to get the
same SCM_TSTAMP_SCHED timestamp without modifying the user-space
application.
A new SKBTX_BPF flag is added to mark skb_shinfo(skb)->tx_flags,
ensuring that the new BPF timestamping and the current user
space's SO_TIMESTAMPING do not interfere with each other.
Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-7-kerneljasonxing@gmail.com
No functional changes here. Only add test to see if the orig_skb
matches the usage of application SO_TIMESTAMPING.
In this series, bpf timestamping and previous socket timestamping
are implemented in the same function __skb_tstamp_tx(). To test
the socket enables socket timestamping feature, this function
skb_tstamp_tx_report_so_timestamping() is added.
In the next patch, another check for bpf timestamping feature
will be introduced just like the above report function, namely,
skb_tstamp_tx_report_bpf_timestamping(). Then users will be able
to know the socket enables either or both of features.
Signed-off-by: Jason Xing <kerneljasonxing@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Link: https://patch.msgid.link/20250220072940.99994-6-kerneljasonxing@gmail.com
After the previous commit is finally safe to revert commit dbae2b0628
("net: skb: introduce and use a single page frag cache"): do it here.
The intended goal of such change was to counter a performance regression
introduced by commit 3226b158e6 ("net: avoid 32 x truesize
under-estimation for tiny skbs").
Unfortunately, the blamed commit introduces another regression for the
virtio_net driver. Such a driver calls napi_alloc_skb() with a tiny
size, so that the whole head frag could fit a 512-byte block.
The single page frag cache uses a 1K fragment for such allocation, and
the additional overhead, under small UDP packets flood, makes the page
allocator a bottleneck.
Thanks to commit bf9f1baa27 ("net: add dedicated kmem_cache for
typical/small skb->head"), this revert does not re-introduce the
original regression. Actually, in the relevant test on top of this
revert, I measure a small but noticeable positive delta, just above
noise level.
The revert itself required some additional mangling due to recent updates
in the affected code.
Suggested-by: Eric Dumazet <edumazet@google.com>
Fixes: dbae2b0628 ("net: skb: introduce and use a single page frag cache")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Sabrina reported the following splat:
WARNING: CPU: 0 PID: 1 at net/core/dev.c:6935 netif_napi_add_weight_locked+0x8f2/0xba0
Modules linked in:
CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted 6.14.0-rc1-net-00092-g011b03359038 #996
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS Arch Linux 1.16.3-1-1 04/01/2014
RIP: 0010:netif_napi_add_weight_locked+0x8f2/0xba0
Code: e8 c3 e6 6a fe 48 83 c4 28 5b 5d 41 5c 41 5d 41 5e 41 5f c3 cc cc cc cc c7 44 24 10 ff ff ff ff e9 8f fb ff ff e8 9e e6 6a fe <0f> 0b e9 d3 fe ff ff e8 92 e6 6a fe 48 8b 04 24 be ff ff ff ff 48
RSP: 0000:ffffc9000001fc60 EFLAGS: 00010293
RAX: 0000000000000000 RBX: ffff88806ce48128 RCX: 1ffff11001664b9e
RDX: ffff888008f00040 RSI: ffffffff8317ca42 RDI: ffff88800b325cb6
RBP: ffff88800b325c40 R08: 0000000000000001 R09: ffffed100167502c
R10: ffff88800b3a8163 R11: 0000000000000000 R12: ffff88800ac1c168
R13: ffff88800ac1c168 R14: ffff88800ac1c168 R15: 0000000000000007
FS: 0000000000000000(0000) GS:ffff88806ce00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: ffff888008201000 CR3: 0000000004c94001 CR4: 0000000000370ef0
DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
Call Trace:
<TASK>
gro_cells_init+0x1ba/0x270
xfrm_input_init+0x4b/0x2a0
xfrm_init+0x38/0x50
ip_rt_init+0x2d7/0x350
ip_init+0xf/0x20
inet_init+0x406/0x590
do_one_initcall+0x9d/0x2e0
do_initcalls+0x23b/0x280
kernel_init_freeable+0x445/0x490
kernel_init+0x20/0x1d0
ret_from_fork+0x46/0x80
ret_from_fork_asm+0x1a/0x30
</TASK>
irq event stamp: 584330
hardirqs last enabled at (584338): [<ffffffff8168bf87>] __up_console_sem+0x77/0xb0
hardirqs last disabled at (584345): [<ffffffff8168bf6c>] __up_console_sem+0x5c/0xb0
softirqs last enabled at (583242): [<ffffffff833ee96d>] netlink_insert+0x14d/0x470
softirqs last disabled at (583754): [<ffffffff8317c8cd>] netif_napi_add_weight_locked+0x77d/0xba0
on kernel built with MAX_SKB_FRAGS=45, where SKB_WITH_OVERHEAD(1024)
is smaller than GRO_MAX_HEAD.
Such built additionally contains the revert of the single page frag cache
so that napi_get_frags() ends up using the page frag allocator, triggering
the splat.
Note that the underlying issue is independent from the mentioned
revert; address it ensuring that the small head cache will fit either TCP
and GRO allocation and updating napi_alloc_skb() and __netdev_alloc_skb()
to select kmalloc() usage for any allocation fitting such cache.
Reported-by: Sabrina Dubroca <sd@queasysnail.net>
Suggested-by: Eric Dumazet <edumazet@google.com>
Fixes: 3948b05950 ("net: introduce a config option to tweak MAX_SKB_FRAGS")
Reviewed-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
In lots of places, bpf_prog pointer is used only for tracing or other
stuff that doesn't modify the structure itself. Same for net_device.
Address at least some of them and add `const` attributes there. The
object code didn't change, but that may prevent unwanted data
modifications and also allow more helpers to have const arguments.
Reviewed-by: Toke Høiland-Jørgensen <toke@redhat.com>
Signed-off-by: Alexander Lobakin <aleksander.lobakin@intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
