linux-kernel - Re: [RPC][PATCH 2.6.20-rc5] limit total vfs page cache

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Date:	Fri, 19 Jan 2007 23:40:20 +0800
From:	"Aubrey Li" <aubreylee@...il.com>
To:	"Vaidyanathan Srinivasan" <svaidy@...ux.vnet.ibm.com>
Cc:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	"Linus Torvalds" <torvalds@...l.org>,
	"Andrew Morton" <akpm@...l.org>,
	"Nick Piggin" <nickpiggin@...oo.com.au>,
	"linux-os (Dick Johnson)" <linux-os@...logic.com>,
	"Robin Getz" <rgetz@...ckfin.uclinux.org>
Subject: Re: [RPC][PATCH 2.6.20-rc5] limit total vfs page cache

On 1/19/07, Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com> wrote:
>
> Hi Aubrey,
>
> I used your patch on my PPC64 box and I do not get expected
> behavior.  As you had requested, I am attaching zoneinfo and meminfo
> dumps:
>
> Please let me know if you need any further data to help me out with
> the test/experiment.
>

Although I have no PPC64 box in hand, I think the logic should be the same.
get_page_from_freelist() is called 5 times in __alloc_pages().

1) alloc_flags = ALLOC_WMARK_LOW | ALLOC_PAGECACHE;
2) alloc_flags = ALLOC_WMARK_MIN | ALLOC_PAGECACHE;
We should have the same result on the first two times get_page_from_freelist().

3) if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE)))
			&& !in_interrupt())
   alloc_flags = ALLOC_NO_WATERMARKS
The case on my platform will never enter this branch. If the branch
occurs on your side,
The limit will be omitted. Because NO watermark, zone_watermark_ok()
will not be checked. memory will be allocated directly.

4)if (likely(did_some_progress)) {
   alloc_flags should include ALLOC_PAGECACHE.
So we should have the same result on this call.

5)	} else if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
   alloc_flags = ALLOC_WMARK_HIGH, without ALLOC_PAGECACHE

This branch will not hit on my case. You may need to check it.

If 3) or 5) occurs on your platform, I think you can easily fix it.
Please confirm it and let me know the result.

Thanks,
-Aubrey
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