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

[Stefan Strogin <s.strogin@partner.samsung.com>]

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@gmail.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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