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writeback: let trace_balance_dirty_pages() take struct dtc as parameter

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Patch series "Fix calculations in trace_balance_dirty_pages() for cgwb", v2.

In my experiment, I found that the output of trace_balance_dirty_pages()
in the cgroup writeback scenario was strange because
trace_balance_dirty_pages() always uses global_wb_domain.dirty_limit for
related calculations instead of the dirty_limit of the corresponding
memcg's wb_domain.

The basic idea of the fix is to store the hard dirty limit value computed
in wb_position_ratio() into struct dirty_throttle_control and use it for
calculations in trace_balance_dirty_pages().


This patch (of 3):

Currently, trace_balance_dirty_pages() already has 12 parameters.  In the
patch #3, I initially attempted to introduce an additional parameter. 
However, in include/linux/trace_events.h, bpf_trace_run12() only supports
up to 12 parameters and bpf_trace_run13() does not exist.

To reduce the number of parameters in trace_balance_dirty_pages(), we can
make it accept a pointer to struct dirty_throttle_control as a parameter. 
To achieve this, we need to move the definition of struct
dirty_throttle_control from mm/page-writeback.c to
include/linux/writeback.h.

Link: https://lkml.kernel.org/r/20250304110318.159567-1-yizhou.tang@shopee.com
Link: https://lkml.kernel.org/r/20250304110318.159567-2-yizhou.tang@shopee.com
Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Tang Yizhou <yizhou.tang@shopee.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Tang Yizhou
2025-03-04 19:03:16 +08:00
committed by Andrew Morton
parent 70478a5534
commit f1ab2831e2
3 changed files with 31 additions and 43 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
include/linux/writeback.h
View File

@@ -313,6 +313,29 @@ static inline void cgroup_writeback_umount(struct super_block *sb)
/*
* mm/page-writeback.c
*/
/* consolidated parameters for balance_dirty_pages() and its subroutines */
struct dirty_throttle_control {
#ifdef CONFIG_CGROUP_WRITEBACK
struct wb_domain *dom;
struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */
#endif
struct bdi_writeback *wb;
struct fprop_local_percpu *wb_completions;
unsigned long avail; /* dirtyable */
unsigned long dirty; /* file_dirty + write + nfs */
unsigned long thresh; /* dirty threshold */
unsigned long bg_thresh; /* dirty background threshold */
unsigned long wb_dirty; /* per-wb counterparts */
unsigned long wb_thresh;
unsigned long wb_bg_thresh;
unsigned long pos_ratio;
bool freerun;
bool dirty_exceeded;
};
void laptop_io_completion(struct backing_dev_info *info);
void laptop_sync_completion(void);
void laptop_mode_timer_fn(struct timer_list *t);

16
include/trace/events/writeback.h
View File

@@ -629,11 +629,7 @@ TRACE_EVENT(bdi_dirty_ratelimit,
TRACE_EVENT(balance_dirty_pages,
TP_PROTO(struct bdi_writeback *wb,
unsigned long thresh,
unsigned long bg_thresh,
unsigned long dirty,
unsigned long bdi_thresh,
unsigned long bdi_dirty,
struct dirty_throttle_control *dtc,
unsigned long dirty_ratelimit,
unsigned long task_ratelimit,
unsigned long dirtied,
@@ -641,7 +637,7 @@ TRACE_EVENT(balance_dirty_pages,
long pause,
unsigned long start_time),
TP_ARGS(wb, thresh, bg_thresh, dirty, bdi_thresh, bdi_dirty,
TP_ARGS(wb, dtc,
dirty_ratelimit, task_ratelimit,
dirtied, period, pause, start_time),
@@ -664,16 +660,16 @@ TRACE_EVENT(balance_dirty_pages,
),
TP_fast_assign(
unsigned long freerun = (thresh + bg_thresh) / 2;
unsigned long freerun = (dtc->thresh + dtc->bg_thresh) / 2;
strscpy_pad(__entry->bdi, bdi_dev_name(wb->bdi), 32);
__entry->limit = global_wb_domain.dirty_limit;
__entry->setpoint = (global_wb_domain.dirty_limit +
freerun) / 2;
__entry->dirty = dirty;
__entry->dirty = dtc->dirty;
__entry->bdi_setpoint = __entry->setpoint *
bdi_thresh / (thresh + 1);
__entry->bdi_dirty = bdi_dirty;
dtc->wb_thresh / (dtc->thresh + 1);
__entry->bdi_dirty = dtc->wb_dirty;
__entry->dirty_ratelimit = KBps(dirty_ratelimit);
__entry->task_ratelimit = KBps(task_ratelimit);
__entry->dirtied = dirtied;

35
mm/page-writeback.c
View File

@@ -120,29 +120,6 @@ EXPORT_SYMBOL(laptop_mode);
struct wb_domain global_wb_domain;
/* consolidated parameters for balance_dirty_pages() and its subroutines */
struct dirty_throttle_control {
#ifdef CONFIG_CGROUP_WRITEBACK
struct wb_domain *dom;
struct dirty_throttle_control *gdtc; /* only set in memcg dtc's */
#endif
struct bdi_writeback *wb;
struct fprop_local_percpu *wb_completions;
unsigned long avail; /* dirtyable */
unsigned long dirty; /* file_dirty + write + nfs */
unsigned long thresh; /* dirty threshold */
unsigned long bg_thresh; /* dirty background threshold */
unsigned long wb_dirty; /* per-wb counterparts */
unsigned long wb_thresh;
unsigned long wb_bg_thresh;
unsigned long pos_ratio;
bool freerun;
bool dirty_exceeded;
};
/*
* Length of period for aging writeout fractions of bdis. This is an
* arbitrarily chosen number. The longer the period, the slower fractions will
@@ -1962,11 +1939,7 @@ static int balance_dirty_pages(struct bdi_writeback *wb,
*/
if (pause < min_pause) {
trace_balance_dirty_pages(wb,
sdtc->thresh,
sdtc->bg_thresh,
sdtc->dirty,
sdtc->wb_thresh,
sdtc->wb_dirty,
sdtc,
dirty_ratelimit,
task_ratelimit,
pages_dirtied,
@@ -1991,11 +1964,7 @@ static int balance_dirty_pages(struct bdi_writeback *wb,
pause:
trace_balance_dirty_pages(wb,
sdtc->thresh,
sdtc->bg_thresh,
sdtc->dirty,
sdtc->wb_thresh,
sdtc->wb_dirty,
sdtc,
dirty_ratelimit,
task_ratelimit,
pages_dirtied,