Date: Sun, 3 Feb 2002 21:48:25 +0000 (GMT) From: Mike Silbersack <silby@silby.com> To: Luigi Rizzo <rizzo@icir.org> Cc: Storms of Perfection <gary@outloud.org>, <thierry@herbelot.com>, <replicator@ngs.ru>, <hackers@FreeBSD.org> Subject: Re: Clock Granularity (kernel option HZ) Message-ID: <20020203214558.T13287-100000@patrocles.silby.com> In-Reply-To: <20020201002017.B48439@iguana.icir.org>
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On Fri, 1 Feb 2002, Luigi Rizzo wrote: > HZ also has an impact on select() behaviour when timeouts are > used (and device drivers using timeouts as well). > A lot of software uses select() with a very short timeout which > is usually rounded up to the next tick. If the author of the software > is unaware of what goes on (likely) there might be negative effects > on performance because such programs stay idle longer than they should. > > cheers > luigi True, I had forgotten about that effect. Ironic, since I was quite annoyed by the limitations of 10ms accuracy last semester. Increasing the resolution of select/usleep is a good argument for increasing the HZ default, but I'm not sure how great the impact would be on slower machines. Mike "Silby" Silbersack To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-hackers" in the body of the message
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