linux-kernel - Re: Performance Stats: Kernel patch

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Message-ID: <461D047B.90800@ru.mvista.com>
Date:	Wed, 11 Apr 2007 19:53:31 +0400
From:	Maxim Uvarov <muvarov@...mvista.com>
To:	Eric Dumazet <dada1@...mosbay.com>
Cc:	linux-kernel@...r.kernel.org, davidsen@....com,
	randy.dunlap@...cle.com, Valdis.Kletnieks@...edu,
	jesper.juhl@...il.com
Subject: Re: Performance Stats: Kernel patch

Eric Dumazet wrote:

 >Please check kernel/sys.c:k_getrusage() to see how getrusage() has to 
sum *lot* of individual fields to get precise process numbers (even 
counting stats for dead threads)

Thanks for helping me and for this link. But it is not enough clear for 
me what do you mean at this time.  Inside of patch I am using 2 default 
counters
task_struct->nivcsw and task_struct->nvcsw. And also one new syscall 
counter. And there is only one way to increment this counter, it is from 
entry.S.

If you are speaking about locks,  in my point of view, they are not 
needed in this code. Because increment syscall counter is atomic for X86 
(just one assembly instruction) and in case with PPC (3 instructions) 
there 1) nothing wrong will not happen in any case 2) only own thread 
can increase it's syscall counter. So here should be not any race 
conditions.

I've tested this patch on x86,x86_64,and ppc_32. And I should work now 
with ppc_64 (I didn't check).
And  also updated description.

Best regards,
Maxim Uvarov.

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