mirrors/linux-stable
1
0
Fork 0
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git synced 2024-09-26 12:26:11 +00:00
Code Issues Releases Wiki Activity

mm: compaction: optimize proactive compaction deferrals

Browse source 
Vlastimil Babka figured out that when fragmentation score didn't go down
across the proactive compaction i.e.  when no progress is made, next wake
up for proactive compaction is deferred for 1 << COMPACT_MAX_DEFER_SHIFT,
i.e.  64 times, with each wakeup interval of
HPAGE_FRAG_CHECK_INTERVAL_MSEC(=500).  In each of this wakeup, it just
decrement 'proactive_defer' counter and goes sleep i.e.  it is getting
woken to just decrement a counter.

The same deferral time can also achieved by simply doing the
HPAGE_FRAG_CHECK_INTERVAL_MSEC << COMPACT_MAX_DEFER_SHIFT thus unnecessary
wakeup of kcompact thread is avoided thus also removes the need of
'proactive_defer' thread counter.

[akpm@linux-foundation.org: tweak comment]

Link: https://lore.kernel.org/linux-fsdevel/88abfdb6-2c13-b5a6-5b46-742d12d1c910@suse.cz/
Link: https://lkml.kernel.org/r/1626869599-25412-1-git-send-email-charante@codeaurora.org
Signed-off-by: Charan Teja Reddy <charante@codeaurora.org>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com>
Acked-by: David Rientjes <rientjes@google.com>
Cc: Nitin Gupta <nigupta@nvidia.com>
Cc: Vinayak Menon <vinmenon@codeaurora.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Charan Teja Reddy 2021-09-02 14:59:56 -07:00 committed by Linus Torvalds
parent 1399af7e54
commit e1e92bfa38
1 changed files with 19 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

29
mm/compaction.c
View file

@ -2885,7 +2885,8 @@ static int kcompactd(void *p)
{
pg_data_t *pgdat = (pg_data_t *)p;
struct task_struct *tsk = current;
unsigned int proactive_defer = 0;
long default_timeout = msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC);
long timeout = default_timeout;
const struct cpumask *cpumask = cpumask_of_node(pgdat->node_id);
@ -2902,23 +2903,30 @@ static int kcompactd(void *p)
trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
kcompactd_work_requested(pgdat),
msecs_to_jiffies(HPAGE_FRAG_CHECK_INTERVAL_MSEC))) {
kcompactd_work_requested(pgdat), timeout)) {
psi_memstall_enter(&pflags);
kcompactd_do_work(pgdat);
psi_memstall_leave(&pflags);
/*
* Reset the timeout value. The defer timeout from
* proactive compaction is lost here but that is fine
* as the condition of the zone changing substantionally
* then carrying on with the previous defer interval is
* not useful.
*/
timeout = default_timeout;
continue;
}
/* kcompactd wait timeout */
/*
* Start the proactive work with default timeout. Based
* on the fragmentation score, this timeout is updated.
*/
timeout = default_timeout;
if (should_proactive_compact_node(pgdat)) {
unsigned int prev_score, score;
if (proactive_defer) {
proactive_defer--;
continue;
}
prev_score = fragmentation_score_node(pgdat);
proactive_compact_node(pgdat);
score = fragmentation_score_node(pgdat);
@ -2926,8 +2934,9 @@ static int kcompactd(void *p)
* Defer proactive compaction if the fragmentation
* score did not go down i.e. no progress made.
*/
proactive_defer = score < prev_score ?
0 : 1 << COMPACT_MAX_DEFER_SHIFT;
if (unlikely(score >= prev_score))
timeout =
default_timeout << COMPACT_MAX_DEFER_SHIFT;
}
}