linux-kernel - Re: Kswapd in 3.2.0-rc5 is a CPU hog

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Date:	Mon, 26 Dec 2011 20:35:46 +0800
From:	Hillf Danton <dhillf@...il.com>
To:	"Nikolay S." <nowhere@...kenden.ath.cx>
Cc:	Dave Chinner <david@...morbit.com>, Michal Hocko <mhocko@...e.cz>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org
Subject: Re: Kswapd in 3.2.0-rc5 is a CPU hog

On Sun, Dec 25, 2011 at 6:21 PM, Nikolay S. <nowhere@...kenden.ath.cx> wrote:
>
> Uhm.., is this patch against 3.2-rc4? I can not apply it. There's no
> mem_cgroup_lru_del_list(), but void mem_cgroup_del_lru_list(). Should I
> place changes there?
>
> And also, -rc7 is here. May the problem be addressed as part of some
> ongoing work? Is there any reason to try -rc7 (the problem requires
> several days of uptime to become obvious)?
>

Sorry, Nikolay, it is not based on the -next, nor on the -rc5(I assumed it was).
The following is based on -next, and if you want to test -rc5, please
grep MEM_CGROUP_ZSTAT mm/memcontrol.c and change it.

Best regard

Hillf
---

--- a/mm/memcontrol.c	Mon Dec 26 20:34:38 2011
+++ b/mm/memcontrol.c	Mon Dec 26 20:37:54 2011
@@ -1076,7 +1076,11 @@ void mem_cgroup_lru_del_list(struct page
 	VM_BUG_ON(!memcg);
 	mz = page_cgroup_zoneinfo(memcg, page);
 	/* huge page split is done under lru_lock. so, we have no races. */
-	MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
+	if (WARN_ON_ONCE(MEM_CGROUP_ZSTAT(mz, lru) <
+				(1 << compound_order(page))))
+		MEM_CGROUP_ZSTAT(mz, lru) = 0;
+	else
+		MEM_CGROUP_ZSTAT(mz, lru) -= 1 << compound_order(page);
 }

 void mem_cgroup_lru_del(struct page *page)
--
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