From mboxrd@z Thu Jan 1 00:00:00 1970 From: bert hubert Date: Sat, 08 Dec 2001 11:52:15 +0000 Subject: Re: [LARTC] HTB not that exact Message-Id: List-Id: References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lartc@vger.kernel.org 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/