linux-kernel - [PATCH 8/9] staging: ion: shrink highmem pages on kswapd

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 26 May 2014 19:05:00 +0900
From:	Heesub Shin <heesub.shin@...sung.com>
To:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:	John Stultz <john.stultz@...aro.org>,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	Colin Cross <ccross@...roid.com>,
	Arve Hjønnevåg <arve@...roid.com>,
	Mitchel Humpherys <mitchelh@...eaurora.org>,
	Daeseok Youn <daeseok.youn@...il.com>,
	Sunghwan Yun <sunghwan.yun@...sung.com>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org,
	Heesub Shin <heesub.shin@...sung.com>
Subject: [PATCH 8/9] staging: ion: shrink highmem pages on kswapd

ION system heap keeps pages in its pool for better performance. When the
system is under memory pressure, slab shrinker calls the callback
registered and then the pages pooled get freed.

When the shrinker is called, it checks gfp_mask and determines whether
the pages from highmem need to be freed or the pages from lowmem.
Usually, slab shrinker is invoked on kswapd context which gfp_mask is
always GFP_KERNEL, so only lowmem pages are released on kswapd context.
This means that highmem pages in the pool are never reclaimed until
direct reclaim occurs. This can be problematic when the page pool holds
excessive amounts of highmem.

For now, the shrinker callback cannot know exactly which zone should be
targeted for reclamation, as enough information are not passed to. Thus,
it makes sense to shrink both lowmem and highmem zone on kswapd context.

Reported-by: Wonseo Choi <wonseo.choi@...sung.com>
Signed-off-by: Heesub Shin <heesub.shin@...sung.com>
---
 drivers/staging/android/ion/ion_page_pool.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/staging/android/ion/ion_page_pool.c b/drivers/staging/android/ion/ion_page_pool.c
index c1cea42b..5864f3d 100644
--- a/drivers/staging/android/ion/ion_page_pool.c
+++ b/drivers/staging/android/ion/ion_page_pool.c
@@ -21,6 +21,7 @@
 #include <linux/list.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/swap.h>
 #include "ion_priv.h"

 static void *ion_page_pool_alloc_pages(struct ion_page_pool *pool)
@@ -118,7 +119,10 @@ int ion_page_pool_shrink(struct ion_page_pool *pool, gfp_t gfp_mask,
 	int freed;
 	bool high;

-	high = !!(gfp_mask & __GFP_HIGHMEM);
+	if (current_is_kswapd())
+		high = 1;
+	else
+		high = !!(gfp_mask & __GFP_HIGHMEM);

 	if (nr_to_scan == 0)
 		return ion_page_pool_total(pool, high);
-- 
1.9.1

--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/