linux-kernel - Re: Regression from 2.6.36

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Message-Id: <20110408142521.4C13197E@pobox.sk>
Date:	Fri, 08 Apr 2011 14:25:21 +0200
From:	"azurIt" <azurit@...ox.sk>
To:	"Changli Gao" <xiaosuo@...il.com>,
	"Eric Dumazet" <eric.dumazet@...il.com>
Cc:	"Américo Wang" <xiyou.wangcong@...il.com>,
	"Jiri Slaby" <jslaby@...e.cz>, <linux-kernel@...r.kernel.org>,
	"Andrew Morton" <akpm@...ux-foundation.org>, <linux-mm@...ck.org>,
	<linux-fsdevel@...r.kernel.org>, "Jiri Slaby" <jirislaby@...il.com>
Subject: Re: Regression from 2.6.36


>azurlt, would you please test the patch attached? Thanks.

This patch fixed the problem, i used 2.6.36.4 for testing. Do you need from me to test also other kernel versions or patches ?

Thank you very much!


______________________________________________________________
> Od: "Changli Gao" <xiaosuo@...il.com>
> Komu: Eric Dumazet <eric.dumazet@...il.com>
> Dátum: 07.04.2011 17:27
> Predmet: Re: Regression from 2.6.36
>
> CC: "Américo Wang" <xiyou.wangcong@...il.com>, "Jiri Slaby" <jslaby@...e.cz>, linux-kernel@...r.kernel.org, "Andrew Morton" <akpm@...ux-foundation.org>, linux-mm@...ck.org, linux-fsdevel@...r.kernel.org, "Jiri Slaby" <jirislaby@...il.com>
>On Thu, Apr 7, 2011 at 8:13 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
>> Le jeudi 07 avril 2011 à 13:57 +0200, Eric Dumazet a écrit :
>>
>>> We had a similar memory problem in fib_trie in the past  : We force a
>>> synchronize_rcu() every XXX Mbytes allocated to make sure we dont have
>>> too much ram waiting to be freed in rcu queues.
>
>I don't think there is too much memory allocated by vmalloc to free.
>My patch should reduce the size of the memory allocated by vmalloc().
>I think the real problem is kfree always returns the memory, whose
>size is aligned to 2^n pages, and more memory are used than before.
>
>>
>> This was done in commit c3059477fce2d956
>> (ipv4: Use synchronize_rcu() during trie_rebalance())
>>
>> It was possible in fib_trie because we hold RTNL lock, so managing
>> a counter was free.
>>
>> In fs case, we might use a percpu_counter if we really want to limit the
>> amount of space.
>>
>> Now, I am not even sure we should care that much and could just forget
>> about this high order pages use.
>
>In normal cases, only a few fds are used, the ftable isn't larger than
>one page, so we should use kmalloc to reduce the memory cost. Maybe we
>should set a upper limit for kmalloc() here. One page?
>
>
>-- 
>Regards,
>Changli Gao(xiaosuo@...il.com)
>
>
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