[PATCH V4 1/3] mm: compaction: optimize proactive compaction deferrals
From: Charan Teja Reddy <hidden>
Date: 2021-06-18 15:21:39
Also in:
linux-fsdevel, linux-mm, lkml
Subsystem:
memory management, memory management - page allocator, the rest · Maintainers:
Andrew Morton, Vlastimil Babka, Linus Torvalds
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(=6) 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.
Suggested-by: Vlastimil Babka <redacted>
Signed-off-by: Charan Teja Reddy <redacted>
---
Changes in V4:
-- Removed the 'proactive_defer' thread counter by optimizing proactive
compaction deferrals.
-- Changes from V1 through V3 doesn't exist.
mm/compaction.c | 29 +++++++++++++++++++----------
1 file changed, 19 insertions(+), 10 deletions(-)
diff --git a/mm/compaction.c b/mm/compaction.c
index 84fde27..bfbcb97 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c@@ -2887,7 +2887,8 @@ 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);
@@ -2904,23 +2905,30 @@ 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);
@@ -2928,8 +2936,9 @@ 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; } }
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation