linux-kernel - Re: [PATCH 1/4] tracing, page-allocator: Add trace events for page allocation and page freeing

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Message-ID: <2f11576a0908072244n45e57c93x6def9f6b64b24133@mail.gmail.com>
Date:	Sat, 8 Aug 2009 14:44:40 +0900
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Mel Gorman <mel@....ul.ie>
Cc:	Larry Woodman <lwoodman@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>, riel@...hat.com,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	LKML <linux-kernel@...r.kernel.org>, linux-mm@...ck.org
Subject: Re: [PATCH 1/4] tracing, page-allocator: Add trace events for page 
	allocation and page freeing

>> > In the NUMA case, this will be true but addressing it involves passing down
>> > an additional argument in the non-tracing case which I wanted to avoid.
>> > As the stacktrace option is available to ftrace, I think I'll drop call_site
>> > altogether as anyone who really needs that information has options.
>>
>> Insted, can we move this tracepoint to alloc_pages_current(), alloc_pages_node() et al ?
>> On page tracking case, call_site information is one of most frequently used one.
>> if we need multiple trace combination, it become hard to use and reduce usefulness a bit.
>>
>
> Ok, lets think about that. The potential points that would need
> annotation are
>
>        o alloc_pages_current
>        o alloc_page_vma
>        o alloc_pages_node
>        o alloc_pages_exact_node
>
> The inlined functions that call those and should preserve the call_site
> are
>
>        o alloc_pages
>
> The slightly lower functions they call are as follows. These cannot
> trigger a tracepoint event because it would look like a duplicate.
>
>        o __alloc_pages_nodemask
>                - called by __alloc_pages
>        o __alloc_pages
>                - called by alloc_page_interleave() but event logged
>                - called by alloc_pages_node but event logged
>                - called by alloc_pages_exact_node but event logged
>
> The more problematic ones are
>
>        o __get_free_pages
>        o get_zeroed_page
>        o alloc_pages_exact
>
> The are all real functions that call down to functions that would log
> events already based on your suggestion - alloc_pages_current() in
> particularly.
>
> Looking at it, it would appear the page allocator API would need a fair
> amount of reschuffling to preserve call_site and not duplicate events or
> else to pass call_site down through the API even in the non-tracing case.
> Minimally, that makes it a standalone patch but it would also need a good
> explanation as to why capturing the stack trace on the event is not enough
> to track the page for things like catching memory leaks.

I agree this is need to some cleanup.
I think I can do that and I can agree your.
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