From: Jamie Lokier <jamie@shareable.org>
To: Arjan van de Ven <arjanv@redhat.com>
Cc: Albert Cahalan <albert@users.sourceforge.net>,
"Randy.Dunlap" <rddunlap@osdl.org>,
Peter Williams <peterw@aurema.com>,
ak@muc.de, Richard.Curnow@superh.com, aeb@cwi.nl,
linux-kernel mailing list <linux-kernel@vger.kernel.org>
Subject: Re: finding out the value of HZ from userspace
Date: Thu, 1 Apr 2004 17:30:47 +0100 [thread overview]
Message-ID: <20040401163047.GD25502@mail.shareable.org> (raw)
In-Reply-To: <20040401160132.GB13294@devserv.devel.redhat.com>
Arjan van de Ven wrote:
> HZ doesn't mean nothing, esp when we go to a tickless kernel...
As explained several times in this thread, HZ is meaningful because it
affects the rounding in select/poll/epoll/setitimer. A few userspace
programs with low jitter soft-RT timing requirements need to
compensate for that rounding and/or deliberately synchronise
themselves with the tick.
Such programs can determine HZ experimentally and lock onto the tick
in the manner of a PLL, but it would be nice to simply be able to
have the value, to reduce the number of control variables.
When we go to a tickless kernel and offer high-resolution timers to
userspace, then it will be irrelevant. Until then, or if the kernel
goes tickless but limits the resolution of timers for efficiency, the
value of HZ is still relevant.
Not to get irritatingly back to the subject of this thread or
anything, but... is the value of HZ reported to userspace anywhere?
Thanks :)
-- Jamie
next prev parent reply other threads:[~2004-04-01 16:31 UTC|newest]
Thread overview: 67+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-03-16 16:14 finding out the value of HZ from userspace Albert Cahalan
2004-03-16 17:22 ` Richard Curnow
2004-03-20 9:56 ` Arjan van de Ven
2004-03-20 14:54 ` Albert Cahalan
2004-03-20 23:58 ` Peter Williams
2004-03-31 21:40 ` Randy.Dunlap
2004-03-31 23:46 ` Albert Cahalan
2004-04-01 15:54 ` Jamie Lokier
2004-04-01 16:01 ` Arjan van de Ven
2004-04-01 16:30 ` Jamie Lokier [this message]
2004-04-01 16:50 ` Richard B. Johnson
2004-04-01 17:01 ` Jamie Lokier
2004-04-01 21:27 ` Michael Buesch
2004-04-02 0:16 ` Peter Williams
2004-04-02 0:07 ` Peter Williams
2004-04-02 0:39 ` Jamie Lokier
2004-04-02 1:44 ` Peter Williams
2004-04-02 18:28 ` Tim Bird
2004-04-02 22:05 ` Peter Williams
2004-04-01 16:12 ` Albert Cahalan
[not found] <1zkOe-Uc-17@gated-at.bofh.it>
[not found] ` <1zl7M-1eJ-43@gated-at.bofh.it>
[not found] ` <1zn9p-3mW-5@gated-at.bofh.it>
[not found] ` <1znj5-3wM-15@gated-at.bofh.it>
[not found] ` <1AaWr-655-7@gated-at.bofh.it>
2004-03-16 2:27 ` Andi Kleen
2004-03-16 5:53 ` Peter Williams
2004-03-16 6:16 ` Andi Kleen
2004-03-16 23:15 ` Peter Williams
2004-03-16 23:56 ` Andi Kleen
2004-03-17 0:15 ` Peter Williams
2004-03-16 9:16 ` Bernd Petrovitsch
2004-03-16 23:45 ` Peter Williams
[not found] <michf@post.tau.ac.il>
2004-03-11 14:17 ` Micha Feigin
2004-03-13 17:24 ` Arjan van de Ven
2004-03-13 19:34 ` John Reiser
2004-03-13 19:38 ` Arjan van de Ven
2004-03-13 22:14 ` Micha Feigin
2004-03-13 22:32 ` Arjan van de Ven
2004-03-14 1:05 ` Micha Feigin
2004-03-14 1:49 ` Andrew Morton
2004-03-14 14:37 ` Micha Feigin
2004-03-16 0:28 ` Peter Williams
2004-03-16 6:33 ` Arjan van de Ven
2004-03-16 23:38 ` Peter Williams
2004-03-20 10:22 ` Arjan van de Ven
2004-03-20 11:28 ` Stefan Smietanowski
2004-03-20 11:41 ` Arjan van de Ven
2004-03-20 23:58 ` Peter Williams
2004-03-21 1:09 ` Tim Schmielau
2004-03-21 1:30 ` Peter Williams
2004-03-21 8:00 ` Kai Henningsen
2004-03-21 10:32 ` Stefan Smietanowski
2004-03-22 22:34 ` Micha Feigin
2004-03-22 23:04 ` Peter Williams
2004-03-25 17:40 ` Jamie Lokier
2004-03-25 23:22 ` Peter Williams
2004-03-27 13:31 ` Jamie Lokier
2004-03-27 23:52 ` Peter Williams
2004-03-28 12:16 ` Jamie Lokier
2004-03-27 21:11 ` Micha Feigin
2004-03-20 23:26 ` Peter Williams
2004-03-13 21:19 ` tabris
2004-03-13 22:10 ` Micha Feigin
2004-03-13 22:41 ` Arjan van de Ven
2004-03-14 1:07 ` Micha Feigin
2004-03-14 18:26 ` John Reiser
2004-03-14 2:45 ` Horst von Brand
2004-03-14 14:39 ` Micha Feigin
2004-03-15 8:17 ` Jamie Lokier
2004-03-16 18:16 ` Mark Gross
2004-03-15 10:13 ` Richard Curnow
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20040401163047.GD25502@mail.shareable.org \
--to=jamie@shareable.org \
--cc=Richard.Curnow@superh.com \
--cc=aeb@cwi.nl \
--cc=ak@muc.de \
--cc=albert@users.sourceforge.net \
--cc=arjanv@redhat.com \
--cc=linux-kernel@vger.kernel.org \
--cc=peterw@aurema.com \
--cc=rddunlap@osdl.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox