From: bert hubert <ahu@ds9a.nl>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] HTB not that exact
Date: Sat, 08 Dec 2001 11:52:15 +0000 [thread overview]
Message-ID: <marc-lartc-100781240318403@msgid-missing> (raw)
In-Reply-To: <marc-lartc-100766696815760@msgid-missing>
On Fri, Dec 07, 2001 at 06:57:39PM +0200, Sami Farin wrote:
> Ahu wrote:
> > Both I think. There are some indications that raising HZ may not work, as it
> > may not raise the resolution of the timers in the Linux Kernel - I am
> > investigating this! So try keeping HZ stable, and raising the size of your
> > bucket.
>
> would it make any difference if you do...
Ok - I've since investigated this. Shapers use timers internally to block
themselves for set periods of time. These timers appear to have HZ
resolution, but a comment in the very good Linux Device Drivers book
http://www.xml.com/ldd/chapter/book/
appeared to indicate that raising HZ would not raise their resolution.
I contacted Jonathan Corbet, one of the authors, and he checked and found
that the book was incorrect: raising HZ *does* increase timer resolution.
> -#define PSCHED_CLOCK_SOURCE PSCHED_JIFFIES
> +#define PSCHED_CLOCK_SOURCE PSCHED_CPU
>
> I didn't see PSCHED_CLOCK_SOURCE in the 2.4routing docs...
> Can you tell more about PSCHED_CLOCK_SOURCE ?
As far as I can see, this only increases the *resolution*, not *precision*.
In other words, you can't specify shorter delays this way but you can
measure a delay that already happened far more precisely.
For example, if you decide to delay for 1 jiffy, 10ms, you may in fact have
waited 14ms. PSCHED_JIFFIES will not see this - 1.4=1 jiffy has passed.
PSCHED_CPU *will* see it, and let the right amount of packets out.
But I'm hoping that Martin Devera can check this for me, devik?
Regards,
bert
--
http://www.PowerDNS.com Versatile DNS Software & Services
Trilab The Technology People
Netherlabs BV / Rent-a-Nerd.nl - Nerd Available -
'SYN! .. SYN|ACK! .. ACK!' - the mating call of the internet
_______________________________________________
LARTC mailing list / LARTC@mailman.ds9a.nl
http://mailman.ds9a.nl/mailman/listinfo/lartc HOWTO: http://ds9a.nl/2.4Routing/
next prev parent reply other threads:[~2001-12-08 11:52 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2001-12-06 19:28 [LARTC] HTB not that exact Stefan Rompf
2001-12-06 19:48 ` bert hubert
2001-12-06 20:33 ` Daniel Ryczek
2001-12-06 21:35 ` Stefan Rompf
2001-12-07 11:46 ` david
2001-12-07 16:57 ` Sami Farin
2001-12-08 8:51 ` Martin Devera
2001-12-08 11:52 ` bert hubert [this message]
2001-12-08 11:53 ` bert hubert
2001-12-08 15:18 ` devik
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=marc-lartc-100781240318403@msgid-missing \
--to=ahu@ds9a.nl \
--cc=lartc@vger.kernel.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