Date: Wed, 6 Aug 2003 00:33:47 -0400 From: Chris BeHanna <chris@behanna.org> To: hackers@freebsd.org Subject: Re: Tuning HZ for semi-realtime applications Message-ID: <200308060033.47237.chris@behanna.org> In-Reply-To: <000501c35a01$6383e040$0300000a@antalus> References: <000501c35a01$6383e040$0300000a@antalus>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sunday 03 August 2003 16:54, Sean Hamilton wrote:
> Greetings,
>
> [...wants to send out a lot of traffic, then read responses 1000
> times per second...is currently using select(2) in a loop...]
>
> Should I set HZ to 1000 (the frequency of my application) or should I set
> it to a much higher value? The CPU is running at around 2 GHz, and I set it
> as high as 50,000 with no problems. However, the granularity of my timeout
> appears to be restricted to 1/1000th of a second.
harti@ already answered this. I have no experience playing with
HZ settings, but his response sounds reasonable enough.
> I would like to use poll(2) instead of select, but it appears to take its
> timeout parameter in milliseconds, which aren't precise enough to keep my
> timing reasonable, especially if I ever need to increase my frequency.
>
> Another option would be calling poll/select with no timeout, in a loop.
> However, this seems like a waste of CPU time.
You could insert an appropriately-sized nanosleep(2) into such a
loop.
--
Chris BeHanna
Software Engineer (Remove "bogus" before responding.)
chris@bogus.behanna.org
Turning coffee into software since 1990.
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200308060033.47237.chris>