Date: Mon, 10 Mar 2003 10:47:30 -0800 From: "Sam Leffler" <sam@errno.com> To: "John Baldwin" <jhb@FreeBSD.org>, "Poul-Henning Kamp" <phk@phk.freebsd.dk> Cc: <src-committers@FreeBSD.org>, <cvs-src@FreeBSD.org>, "Nate Lawson" <nate@root.org> Subject: Re: cvs commit: src/sys/sys devicestat.h Message-ID: <15bf01c2e735$825f1eb0$52557f42@errno.com> References: <3039.1047321059@critter.freebsd.dk>
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> This is disk statistics, it's not really worth that effort. The
> data in the structure will not get corrupted, bue one of our
> readings may. So what...
All the more reason why I question the complexity. Are there really going
to be that many clients polling for statistics that using a system call is
bad?
FWIW I worked on a real-time event/statistics package for IRIX. There were
per-cpu queues of events mapped into user-space. Lots of atomic ops and
such to get a lock-free mechanism with guaranteed consistency of results
(e.g. this was supposedly used to monitor real-time data collection sites
like physical plants). Aggregating the per-cpu streams was a pain.
For something like the above I could understand the added complexity. For
disk stats for top, etc, no.
Sam
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