Date: Fri, 9 Sep 2011 21:43:47 +0800 From: Paul Ambrose <ambrosehua@gmail.com> To: Alexander Best <arundel@freebsd.org> Cc: freebsd-hackers@freebsd.org Subject: Re: excessive use of gettimeofday(2) and other syscalls Message-ID: <CAMwoQQ46p8oDFVX==Unrf2k2Mh70vtU5HniV7PZYLY5tBujHjA@mail.gmail.com> In-Reply-To: <20110907151543.GA63310@freebsd.org> References: <20110906220115.GA25048@freebsd.org> <CAHRgBhRe8n%2BV3nSzRn4_fctHB1nie2ACk7oRVOPJqqKaMUgKrg@mail.gmail.com> <CAF6rxg=kzHP4zr_=LGnJDUQu-xEwgpy6QN=Lk4jqXa6hs=epKg@mail.gmail.com> <CAHRgBhT%2BKi%2BYPiK%2Bhn=fJ91eA=31tOaTPe_5xLSHQawa=%2BFD0Q@mail.gmail.com> <CAHwLALMwOu8wc5W03dar5fhkWkjN6f7eDGAT4a1u%2BK4eHHSsng@mail.gmail.com> <20110907061741.GC96277@server.vk2pj.dyndns.org> <20110907151543.GA63310@freebsd.org>
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what version of chromium are you using? I use chromium-13.0.782.215 on amd64 8.2-stable, the gettimeofday call is far less than 20000 per second, about 20 per second, but I notice old version has this bug, but latest version has fixed it. Maybe you should update your chromium and try again. Firefox 5 and 6 has more gettimeofday call than 20000 per second on my amd64-8.2-stable box. 2011/9/7 Alexander Best <arundel@freebsd.org> > On Wed Sep 7 11, Peter Jeremy wrote: > > On 2011-Sep-06 16:44:48 -0600, Manish Vachharajani < > manishv@lineratesystems.com> wrote: > > >Under 7.3 (haven't checked 8 or 9) this issue crops up because the > > >time system call calls gettimeofday under the hood (see > > >lib/libc/gen/time.c). As a result, the kernel tries to get an > > >accurate subsecond resolution time that simply gets chopped to the > > >nearest second. > > > > Under 8.x and later, time(3) uses clock_gettime(CLOCK_SECOND,...) > > rather than gettimeofday(). This is intended to be much cheaper > > than gettimeofday(). > > > > On 2011-Sep-06 21:15:55 -0400, Rayson Ho <raysonlogin@gmail.com> wrote: > > >IMO, the time returned by gettimeofday does not need to be high > > >precision. There are higher resolution time APIs on Linux and I > > >believe the application programmers know when to use the slower but > > >more accurate clock API. > > > > There are 3 standard APIs for returning time of day: > > time(3) provides second precision > > gettimeofday(2) provides microsecond precision > > clock_gettime(2) provides nanosecond precision > > > > By default, FreeBSD attempts to provide resolution as close as > > possible to the precision - which makes the 2 system calls fairly > > expensive. In order to reduce the cost where the resolution isn't > > important, FreeBSD provides several non-standard clock types for > > clock_gettime(2). This approach differs from Linux - and it seems > > that there is a non-trivial body of code that assumes that calling > > gettimeofday() is very cheap. > > > > There is probably a good case for an API that provides a resolution > > of the order of a tick but there is no standard for this. > > chromium is triggering ~20.000 gettimeofday(2) calls per second on my > machine. > i'm running CURRENT on amd64. > > cheers. > alex > > > > > -- > > Peter Jeremy > > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" >
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