linux-kernel - Re: [PATCH] mm: cma: add trace events for CMA allocations and freeings

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Message-id: <551D3E73.9070405@partner.samsung.com>
Date:	Thu, 02 Apr 2015 16:04:51 +0300
From:	Stefan Strogin <s.strogin@...tner.samsung.com>
To:	Joonsoo Kim <iamjoonsoo.kim@....com>
Cc:	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Steven Rostedt <rostedt@...dmis.org>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Michal Nazarewicz <mina86@...a86.com>,
	aneesh.kumar@...ux.vnet.ibm.com,
	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Sasha Levin <sasha.levin@...cle.com>,
	Dmitry Safonov <d.safonov@...tner.samsung.com>,
	Pintu Kumar <pintu.k@...sung.com>,
	Laura Abbott <lauraa@...eaurora.org>,
	Dyasly Sergey <s.dyasly@...sung.com>,
	Vyacheslav Tyrtov <v.tyrtov@...sung.com>,
	Aleksei Mateosian <a.mateosian@...sung.com>, gioh.kim@....com,
	stefan.strogin@...il.com
Subject: Re: [PATCH] mm: cma: add trace events for CMA allocations and freeings

Hello Joonsoo,

On 02/04/15 10:33, Joonsoo Kim wrote:
> Hello,
> 
> On Wed, Apr 01, 2015 at 04:31:43PM +0300, Stefan Strogin wrote:
>> Add trace events for cma_alloc() and cma_release().
>>
>> The cma_alloc tracepoint is used both for successful and failed allocations,
>> in case of allocation failure pfn=-1UL is stored and printed.
>>
>> Signed-off-by: Stefan Strogin <stefan.strogin@...il.com>
>> ---
>>
>> Took out from the patch set "mm: cma: add some debug information for CMA" v4
>> (http://thread.gmane.org/gmane.linux.kernel.mm/129903) because of probable
>> uselessness of the rest of the patches.
> 
> I think that patch 5/5 in previous submission is handy and
> simple to merge. Although we can calculate it by using bitmap,
> it would be good to get that information(used size and maxchunk size)
> directly.

Well, then I can send the patch 5/5 once more, this time singly.

> 
>> @@ -414,6 +416,8 @@ struct page *cma_alloc(struct cma *cma, unsigned int count, unsigned int align)
>>  		start = bitmap_no + mask + 1;
>>  	}
>>  
>> +	trace_cma_alloc(page ? pfn : -1UL, page, count);
>> +
> 
> I think that tracing align is also useful.
> Is there any reason not to include it?

In our case (DMA) alignment is easily calculated from the allocation
size and CONFIG_CMA_ALIGNMENT. But I think you're right, e.g. it may be
not so obvious on powerpc kvm? Anyway it won't be a shortcoming if we
trace 'align' too.

> 
> Thanks.

Thank you for the reply.
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