linux-kernel - [PATCH V4 3/3] mm: compaction: fix wakeup logic of proactive compaction

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Date:   Fri, 18 Jun 2021 20:48:55 +0530
From:   Charan Teja Reddy <charante@...eaurora.org>
To:     akpm@...ux-foundation.org, vbabka@...e.cz, corbet@....net,
        mcgrof@...nel.org, keescook@...omium.org, yzaikin@...gle.com,
        osalvador@...e.de, rientjes@...gle.com, mchehab+huawei@...nel.org,
        lokeshgidra@...gle.com, andrew.a.klychkov@...il.com,
        xi.fengfei@....com, nigupta@...dia.com,
        dave.hansen@...ux.intel.com, famzheng@...zon.com,
        mateusznosek0@...il.com, oleksandr@...hat.com, sh_def@....com
Cc:     linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, linux-fsdevel@...r.kernel.org,
        Charan Teja Reddy <charante@...eaurora.org>
Subject: [PATCH V4 3/3] mm: compaction: fix wakeup logic of proactive compaction

Currently, proactive compaction tries to get triggered for every
HPAGE_FRAG_CHECK_INTERVAL_MSEC(=500msec) even when proactive compaction
is disabled with sysctl.compaction_proactiveness = 0. This results in
kcompactd thread wakes up and goes to sleep for every 500msec with out
the need of doing proactive compaction. Though this doesn't have any
overhead, few cpu cycles can be saved by avoid of waking up kcompactd
thread for proactive compaction when it is disabled.

Signed-off-by: Charan Teja Reddy <charante@...eaurora.org>
---
 -- Changes in V4:
       o No functional changes from V3.
 -- Changes in V3:
       o Fix wake up logic in proactive compaction.
 -- Changes in V2 through V2 doesn't exist.

 mm/compaction.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/mm/compaction.c b/mm/compaction.c
index 7672be3..44a232a 100644
--- a/mm/compaction.c
+++ b/mm/compaction.c
@@ -2928,6 +2928,8 @@ static int kcompactd(void *p)
 	while (!kthread_should_stop()) {
 		unsigned long pflags;
 
+		if (!sysctl_compaction_proactiveness)
+			timeout = MAX_SCHEDULE_TIMEOUT;
 		trace_mm_compaction_kcompactd_sleep(pgdat->node_id);
 		if (wait_event_freezable_timeout(pgdat->kcompactd_wait,
 			kcompactd_work_requested(pgdat), timeout) &&
-- 
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