Date: Fri, 28 Oct 2005 12:50:16 +0200 From: "Poul-Henning Kamp" <phk@phk.freebsd.dk> To: David Xu <davidxu@freebsd.org> Cc: Pertti Kosunen <pertti.kosunen@pp.nic.fi>, current@freebsd.org, "Yuriy N. Shkandybin" <jura@networks.ru> Subject: Re: Timers and timing, was: MySQL Performance 6.0rc1 Message-ID: <31223.1130496616@critter.freebsd.dk> In-Reply-To: Your message of "Fri, 28 Oct 2005 18:43:10 %2B0800." <436200BE.70604@freebsd.org>
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In message <436200BE.70604@freebsd.org>, David Xu writes: >Poul-Henning Kamp wrote: >> In message <4361FDBE.7000500@freebsd.org>, David Xu writes: >> >> >> the correct way to optimize this would be to add a time(2) systemcall >> which returns the value of the kernel global time_second. >> > >Can we make a page in kernel address space which is readable my user >code? put the variable in the page, I know read an integer is atomic-op, >needn't lock, so syscall is not needed. We have often talked about doing something like that, but so far nobody has come up with a (sensible) implementation. Please thing _very_ carefully about the implications for libc versioning before hacking up a patch. -- Poul-Henning Kamp | UNIX since Zilog Zeus 3.20 phk@FreeBSD.ORG | TCP/IP since RFC 956 FreeBSD committer | BSD since 4.3-tahoe Never attribute to malice what can adequately be explained by incompetence.
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