linux-kernel - Re: [PATCH] Debugging: Keep track of page owners

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Message-ID: <50C274B1.90408@linux.vnet.ibm.com>
Date:	Fri, 07 Dec 2012 14:58:57 -0800
From:	Dave Hansen <dave@...ux.vnet.ibm.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
CC:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH] Debugging: Keep track of page owners

On 12/07/2012 02:44 PM, Andrew Morton wrote:
> AFACIT that difference was undescribed.  I can see that the new version
> uses the stack-tracing infrastructure, but the change to
> pagetypeinfo_showmixedcount_print() is a mystery.

Ahhh, I assume you're talking about this hunk:

>> @@ -976,10 +976,7 @@ static void pagetypeinfo_showmixedcount_print(struct seq_file *m,
>>  
>>                         pagetype = allocflags_to_migratetype(page->gfp_mask);
>>                         if (pagetype != mtype) {
>> -                               if (is_migrate_cma(pagetype))
>> -                                       count[MIGRATE_MOVABLE]++;
>> -                               else
>> -                                       count[mtype]++;
>> +                               count[mtype]++;
>>                                 break;
>>                         }

That was to fix the comment that Laura Abbott made about it miscounting
MIGRATE_CMA pages.

My patch-sending scripts were choking a bit on the text description in
your patch.  I'm using a long-ago-forked copy of your patch-utils and
the DESC/EDESC in the patch I imported is giving them fits when I send
via email and stripping large parts of the description.  I'm happy to
resend via email, too, but here, the raw patch (will the full description):

	https://www.sr71.net/~dave/linux/pageowner.patch

The important description that the scripts managed to strip out when
emailed was this:

Updated 12/4/2012 - should apply to 3.7 kernels.  I did a quick
sniff-test to make sure that this boots and produces some sane
output, but it's not been exhaustively tested.

 * Moved file over to debugfs (no reason to keep polluting /proc)
 * Now using generic stack tracking infrastructure
 * Added check for MIGRATE_CMA pages to explicitly count them
   as movable.

The new snprint_stack_trace() probably belongs in its own patch
if this were to get merged, but it won't kill anyone as it stands.

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