| Message ID | 1626869599-25412-1-git-send-email-charante@codeaurora.org (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | [resend] mm: compaction: optimize proactive compaction deferrals | expand |
On Wed, 21 Jul 2021 17:43:19 +0530 Charan Teja Reddy <charante@codeaurora.org> wrote: > 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. > > @@ -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 by > + * proactive compaction can effectively lost > + * here but that is fine as the condition of the > + * zone changed substantionally and carrying on > + * with the previous defer is not useful. > + */ > + timeout = default_timeout; > continue; I find this comment hard to follow. Is this better? --- a/mm/compaction.c~mm-compaction-optimize-proactive-compaction-deferrals-fix +++ a/mm/compaction.c @@ -2909,11 +2909,11 @@ static int kcompactd(void *p) kcompactd_do_work(pgdat); psi_memstall_leave(&pflags); /* - * Reset the timeout value. The defer timeout by - * proactive compaction can effectively lost - * here but that is fine as the condition of the - * zone changed substantionally and carrying on - * with the previous defer is not useful. + * 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;
On 7/21/21 10:18 PM, Andrew Morton wrote: > On Wed, 21 Jul 2021 17:43:19 +0530 Charan Teja Reddy <charante@codeaurora.org> wrote: > >> 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. Acked-by: Vlastimil Babka <vbabka@suse.cz> >> >> @@ -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 by >> + * proactive compaction can effectively lost >> + * here but that is fine as the condition of the >> + * zone changed substantionally and carrying on >> + * with the previous defer is not useful. >> + */ >> + timeout = default_timeout; >> continue; > > I find this comment hard to follow. Is this better? Yes, thanks. > --- a/mm/compaction.c~mm-compaction-optimize-proactive-compaction-deferrals-fix > +++ a/mm/compaction.c > @@ -2909,11 +2909,11 @@ static int kcompactd(void *p) > kcompactd_do_work(pgdat); > psi_memstall_leave(&pflags); > /* > - * Reset the timeout value. The defer timeout by > - * proactive compaction can effectively lost > - * here but that is fine as the condition of the > - * zone changed substantionally and carrying on > - * with the previous defer is not useful. > + * 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; > _ >
On 7/21/21 6:13 AM, Charan Teja Reddy wrote: > 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. > > Link: https://lore.kernel.org/linux-fsdevel/88abfdb6-2c13-b5a6-5b46-742d12d1c910@suse.cz/ > Signed-off-by: Charan Teja Reddy <charante@codeaurora.org> Reviewed-by: Khalid Aziz <khalid.aziz@oracle.com> > --- > Changes in V1: > o Removed the 'proactive_defer' thread counter by optimizing proactive > o This is a resend as earlier it was clubbed with other changes posted > at https://lore.kernel.org/patchwork/patch/1448789/ > > mm/compaction.c | 29 +++++++++++++++++++---------- > 1 file changed, 19 insertions(+), 10 deletions(-) > > diff --git a/mm/compaction.c b/mm/compaction.c > index 621508e..db00dbf 100644 > --- a/mm/compaction.c > +++ b/mm/compaction.c > @@ -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 by > + * proactive compaction can effectively lost > + * here but that is fine as the condition of the > + * zone changed substantionally and carrying on > + * with the previous defer 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; > } > } > >
On Wed, 21 Jul 2021, Charan Teja Reddy wrote: > 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. > > Link: https://lore.kernel.org/linux-fsdevel/88abfdb6-2c13-b5a6-5b46-742d12d1c910@suse.cz/ > Signed-off-by: Charan Teja Reddy <charante@codeaurora.org> With Andrew's comment fixup: Acked-by: David Rientjes <rientjes@google.com> Thanks, Charan.
diff --git a/mm/compaction.c b/mm/compaction.c index 621508e..db00dbf 100644 --- a/mm/compaction.c +++ b/mm/compaction.c @@ -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 by + * proactive compaction can effectively lost + * here but that is fine as the condition of the + * zone changed substantionally and carrying on + * with the previous defer 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; } }
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. Link: https://lore.kernel.org/linux-fsdevel/88abfdb6-2c13-b5a6-5b46-742d12d1c910@suse.cz/ Signed-off-by: Charan Teja Reddy <charante@codeaurora.org> --- Changes in V1: o Removed the 'proactive_defer' thread counter by optimizing proactive o This is a resend as earlier it was clubbed with other changes posted at https://lore.kernel.org/patchwork/patch/1448789/ mm/compaction.c | 29 +++++++++++++++++++---------- 1 file changed, 19 insertions(+), 10 deletions(-)