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Message-ID: <p73bqir7myp.fsf@bingen.suse.de> Date: 17 Mar 2007 19:18:38 +0100 From: Andi Kleen <andi@...stfloor.org> To: Tomasz Noiński <noix@...ere.pl> Cc: linux-kernel@...r.kernel.org, timm@....uni-heidelberg.de, arne.wiebalck@....uni-heidelberg.de Subject: Re: more precise CPU time accounting for x86 Tomasz Noiński <noix@...ere.pl> writes: > Hi, > > I've written a small patch for more precise process CPU time accounting > for processors with TSC. > > Currently, accounting is sample-based and it can be fooled by, for > example, a process that always gives away the rest of it's timeslice. RDTSC is unfortunately quite slow on some CPUs. But we already use it in schedule for sched_clock(). I think an interesting approach would be to use this information and just sum it up in the task_struct. This would still not account for interrupts and system time separately, but should be relatively cheap and give more accurate time. Drawback would be that user tools would need to be updated to read a "sys+user" count. BTW perfctrs on most x86 CPUs can count user/kernel separately, unfortunately it is hard to find a performance counter that matches real time well enough and they couldn't easily separate interrupts vs systime belonging to the process. -Andi - 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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