linux-kernel - Re: The VFS cache is not freed when there is not enough free memory to allocate

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Message-ID: <6d6a94c50612010200t2c9dfc36m603ddc4948285bf@mail.gmail.com>
Date:	Fri, 1 Dec 2006 18:00:53 +0800
From:	Aubrey <aubreylee@...il.com>
To:	"Nick Piggin" <nickpiggin@...oo.com.au>
Cc:	"Sonic Zhang" <sonic.adi@...il.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	vapier.adi@...il.com
Subject: Re: The VFS cache is not freed when there is not enough free memory to allocate

On 12/1/06, Nick Piggin <nickpiggin@...oo.com.au> wrote:
>
> The pattern you are seeing here is probably due to the page allocator
> always retrying process context allocations which are <= order 3 (64K
> with 4K pages).
>
> You might be able to increase this limit a bit for your system, but it
> could easily cause problems. Especially fragmentation on nommu systems
> where the anonymous memory cannot be paged out.

Thanks for your clue. I found increasing this limit could really help
my test cases.
When MemFree < 8M, and the test case request 1M * 8 times, the
allocation can be sucessful after 81 times rebalance, :). So far I
haven't found any issue.

If I make a patch to move this parameter to be tunable in the proc
filesystem on nommu case, is it acceptable?

Thanks,
-Aubrey
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