Re: top hogs CPU in 2.6: kallsyms_lookup is very slow

From: Denis Vlasenko (vda_at_port.imtp.ilyichevsk.odessa.ua)
Date: 09/17/04

  • Next message: William Lee Irwin III: "Re: top hogs CPU in 2.6: kallsyms_lookup is very slow" 
    To: William Lee Irwin III <wli@holomorphy.com>
Date:	Fri, 17 Sep 2004 12:01:15 +0300

    On Thursday 16 September 2004 15:17, William Lee Irwin III wrote:
    > At some point in the past, I wrote:
    > >> As for all syscalls/etc. being slower by 50%-100%, I suggest toning
    >
    > On Thu, Sep 16, 2004 at 02:57:08PM +0300, Denis Vlasenko wrote:
    > > s/all/many/:
    > > uname <0.000142> ? ? ? ? ? ? ? uname <0.000217> 25% slower
    > > brk <0.000176> ? ? ? ? ? ? ? ? brk <0.000174> no change
    > > open <0.000218> ? ? ? ? ? ? ? ?open <0.000335> 33% slower
    > > fstat64 <0.000104> ? ? ? ? ? ? fstat64 <0.000191> 90% slower
    > > or maybe strace simply isn't very accurate and adds signinficant
    > > noise to the measured delta?
    >
    > Could you try to estimate the resolution of whatever timer strace uses?
    >
    > At some point in the past, I wrote:
    > >> down HZ (we desperately need to go tickless) and seeing if it persists.
    > >> Also please check that time isn't twice as fast as it should be in 2.6.
    >
    > On Thu, Sep 16, 2004 at 02:57:08PM +0300, Denis Vlasenko wrote:
    > > I recompiled 2.6 with HZ=100. It's not it.
    > > Time is running normally too.
    >
    > Did the kallsyms patches reduce the cpu overhead from get_wchan()?

    Yes. top does not hog CPU anymore. It takes even a liitle bit *less*
    CPU than in 2.4 now. 

    --
vda
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  • Next message: William Lee Irwin III: "Re: top hogs CPU in 2.6: kallsyms_lookup is very slow"

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