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Date: Tue, 14 Nov 2006 14:50:07 +0100 From: Eric Dumazet <dada1@...mosbay.com> To: Andrew Morton <akpm@...l.org>, Ingo Molnar <mingo@...e.hu> Cc: linux-kernel@...r.kernel.org, tglx@...utronix.de Subject: Re: 2.6.19-rc5-mm2 On Tuesday 14 November 2006 10:41, Andrew Morton wrote: > Presently at > > http://userweb.kernel.org/~akpm/2.6.19-rc5-mm2/ > > and will appear later at > > ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.19-rc5/2. >6.19-rc5-mm2/ Hi all I noticed a slowdown (3%) on a io micro-benchmark on my machine with 2.6.19-rc5-mm2 It appears time-uninline-jiffiesh.patch is sub-optimal at least for current compilers (tested gcc-4.0.4 here) May I suggest : 1) make sure jiffies_to_usecs() is defined before being used in timespec_trunc() : Compiler will just optimize away not *needed* code. OR : 2) Revert to inline versions of four functions jiffies_to_msecs(), jiffies_to_usecs(), msecs_to_jiffies() and usecs_to_jiffies() . IMHO there is litle gain to call a function just to perform so basic arithmetics, that sometime compiler can perform at compilation time. OR 3) replace (jiffies_to_usecs(1) * 1000) by (NSEC_PER_SEC / HZ) With current patch, timespec_trunc() is not anymore a tail function. struct timespec timespec_trunc(struct timespec t, unsigned gran) { if (gran <= jiffies_to_usecs(1) * 1000) { Much better here to have : if (gran < SOME_CONSTANT) Thank you Eric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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