Messages in this thread | | | Subject | Re: [PATCH resend] mm: compaction: optimize proactive compaction deferrals | From | Khalid Aziz <> | Date | Wed, 21 Jul 2021 16:35:05 -0600 |
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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; > } > } > >
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