mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2025-04-06 00:16:18 +00:00
Code Issues Packages Projects Releases Wiki Activity

writeback: fix calculations in trace_balance_dirty_pages() for cgwb

Browse Source 
In the commit dcc25ae76eb7 ("writeback: move global_dirty_limit into
wb_domain") of the cgroup writeback backpressure propagation patchset,
Tejun made some adaptations to trace_balance_dirty_pages() for cgroup
writeback.  However, this adaptation was incomplete and Tejun missed
further adaptation in the subsequent patches.

In the cgroup writeback scenario, if sdtc in balance_dirty_pages() is
assigned to mdtc, then upon entering trace_balance_dirty_pages(),
__entry->limit should be assigned based on the dirty_limit of the
corresponding memcg's wb_domain, rather than global_wb_domain.

To address this issue and simplify the implementation, introduce a 'limit'
field in struct dirty_throttle_control to store the hard_limit value
computed in wb_position_ratio() by calling hard_dirty_limit().  This field
will then be used in trace_balance_dirty_pages() to assign the value to
__entry->limit.

Link: https://lkml.kernel.org/r/20250304110318.159567-4-yizhou.tang@shopee.com
Fixes: dcc25ae76eb7 ("writeback: move global_dirty_limit into wb_domain")
Signed-off-by: Tang Yizhou <yizhou.tang@shopee.com>
Acked-by: Tejun Heo <tj@kernel.org>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Christian Brauner <brauner@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: "Masami Hiramatsu (Google)" <mhiramat@kernel.org>
Cc: Matthew Wilcow (Oracle) <willy@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Tang Yizhou 2025-03-04 19:03:18 +08:00 committed by Andrew Morton
parent 28c24ef9e0
commit 6cc4c3aa71
3 changed files with 4 additions and 4 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

1
include/linux/writeback.h
View File

@ -326,6 +326,7 @@ struct dirty_throttle_control {
unsigned long dirty; /* file_dirty + write + nfs */
unsigned long thresh; /* dirty threshold */
unsigned long bg_thresh; /* dirty background threshold */
unsigned long limit; /* hard dirty limit */
unsigned long wb_dirty; /* per-wb counterparts */
unsigned long wb_thresh;

5
include/trace/events/writeback.h
View File

@ -663,9 +663,8 @@ TRACE_EVENT(balance_dirty_pages,
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->limit = dtc->limit;
__entry->setpoint = (dtc->limit + freerun) / 2;
__entry->dirty = dtc->dirty;
__entry->wb_setpoint = __entry->setpoint *
dtc->wb_thresh / (dtc->thresh + 1);

2
mm/page-writeback.c
View File

@ -1072,7 +1072,7 @@ static void wb_position_ratio(struct dirty_throttle_control *dtc)
struct bdi_writeback *wb = dtc->wb;
unsigned long write_bw = READ_ONCE(wb->avg_write_bandwidth);
unsigned long freerun = dirty_freerun_ceiling(dtc->thresh, dtc->bg_thresh);
unsigned long limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh);
unsigned long limit = dtc->limit = hard_dirty_limit(dtc_dom(dtc), dtc->thresh);
unsigned long wb_thresh = dtc->wb_thresh;
unsigned long x_intercept;
unsigned long setpoint; /* dirty pages' target balance point */