From: Jarek Poplawski <jarkao2@gmail•com>
To: Denys Fedoryschenko <denys@visp•net.lb>
Cc: Stephen Hemminger <shemminger@linux-foundation•org>,
netdev@vger•kernel.org
Subject: Re: [PATCH] [RESEND] iproute2 : invalid burst/cburst calculation with hrtimers
Date: Thu, 5 Feb 2009 07:38:32 +0000 [thread overview]
Message-ID: <20090205073832.GA4305@ff.dom.local> (raw)
In-Reply-To: <200902050124.05969.denys@visp.net.lb>
On Thu, Feb 05, 2009 at 01:24:05AM +0200, Denys Fedoryschenko wrote:
> On Thursday 05 February 2009 00:49:29 Jarek Poplawski wrote:
> > On Thu, Feb 05, 2009 at 12:26:46AM +0200, Denys Fedoryschenko wrote:
> > ...
> >
> > > Maybe we can put note in documentation or even htb help output, that user
> > > can increase precision with hrtimers enabled, by setting HZ variable?
> >
> > Hmm... I rather meant using burst and cburst params. But hrtimers are
> > very hardware dependent, so it's hard to advise anything.
> >
> > Jarek P.
>
> By default burst/cburst calculated depends on timer resolution, as i
> understood, by taking 4th parameter of /proc/net/psched, which as i
> understood - precision of hrtimer .
>
> With hrtimers it is nanosecond resolution, precision is very high, but
> overhead too high too. And as i understand, maybe it can be problem, that htb
> still uses HZ variable in some cases like:
> return q->now + 2 * PSCHED_TICKS_PER_SEC / HZ;
I think HZ doesn't matter much in this place, because if it's ever
triggered there is something really wrong and precision is lost.
Anyway, this place was changed a bit in net-next.
I guess I could misunderstand your previous question. If you mean this
previous thread, then yes, IMHO CONFIG_HZ should matter for precision
(especially places where similar loops use all such jiffies in "normal"
situations). On the other hand, maybe I'm wrong, but using HZ 1000
with HIGH_RES_TIMERS looks quite obvious to me...
Jarek P.
next prev parent reply other threads:[~2009-02-05 7:38 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-02-02 17:26 [PATCH] [RESEND] iproute2 : invalid burst/cburst calculation with hrtimers Denys Fedoryschenko
2009-02-02 18:07 ` Stephen Hemminger
2009-02-02 18:21 ` Denys Fedoryschenko
2009-02-04 21:20 ` Jarek Poplawski
2009-02-04 21:53 ` Jarek Poplawski
2009-02-04 22:26 ` Denys Fedoryschenko
2009-02-04 22:49 ` Jarek Poplawski
2009-02-04 23:24 ` Denys Fedoryschenko
2009-02-05 7:38 ` Jarek Poplawski [this message]
2009-02-05 9:01 ` Denys Fedoryschenko
2009-02-05 10:08 ` Jarek Poplawski
2009-02-05 11:09 ` Denys Fedoryschenko
2009-02-05 11:56 ` Jarek Poplawski
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=20090205073832.GA4305@ff.dom.local \
--to=jarkao2@gmail$(echo .)com \
--cc=denys@visp$(echo .)net.lb \
--cc=netdev@vger$(echo .)kernel.org \
--cc=shemminger@linux-foundation$(echo .)org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
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