linux-kernel - [PATCH] lowmemorykiller: Avoid excessive/redundant calling of LMK

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Date:	Mon, 12 Jan 2015 21:49:14 +0530
From:	Chintan Pandya <cpandya@...eaurora.org>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Weijie Yang <weijie.yang@...sung.com>,
	David Rientjes <rientjes@...gle.com>
Cc:	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	akpm@...ux-foundation.org, linux-mm@...ck.org,
	Chintan Pandya <cpandya@...eaurora.org>
Subject: [PATCH] lowmemorykiller: Avoid excessive/redundant calling of LMK

The global shrinker will invoke lowmem_shrink in a loop.
The loop will be run (total_scan_pages/batch_size) times.
The default batch_size will be 128 which will make
shrinker invoking 100s of times. LMK does meaningful
work only during first 2-3 times and then rest of the
invocations are just CPU cycle waste. Fix that by returning
to the shrinker with SHRINK_STOP when LMK doesn't find any
more work to do. The deciding factor here is, no process
found in the selected LMK bucket or memory conditions are
sane.

Signed-off-by: Chintan Pandya <cpandya@...eaurora.org>
---
 drivers/staging/android/lowmemorykiller.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/lowmemorykiller.c b/drivers/staging/android/lowmemorykiller.c
index b545d3d..5bf483f 100644
--- a/drivers/staging/android/lowmemorykiller.c
+++ b/drivers/staging/android/lowmemorykiller.c
@@ -110,7 +110,7 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
 	if (min_score_adj == OOM_SCORE_ADJ_MAX + 1) {
 		lowmem_print(5, "lowmem_scan %lu, %x, return 0\n",
 			     sc->nr_to_scan, sc->gfp_mask);
-		return 0;
+		return SHRINK_STOP;
 	}
 
 	selected_oom_score_adj = min_score_adj;
@@ -163,6 +163,9 @@ static unsigned long lowmem_scan(struct shrinker *s, struct shrink_control *sc)
 		set_tsk_thread_flag(selected, TIF_MEMDIE);
 		send_sig(SIGKILL, selected, 0);
 		rem += selected_tasksize;
+	} else {
+		rcu_read_unlock();
+		return SHRINK_STOP;
 	}
 
 	lowmem_print(4, "lowmem_scan %lu, %x, return %lu\n",
-- 
Chintan Pandya

QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member of the Code Aurora Forum, hosted by The Linux Foundation

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