Date: Mon, 24 Dec 2007 08:49:36 -0700 From: Brett Glass <brett@lariat.net> To: Scott Long <scottl@samsco.org> Cc: stable@freebsd.org Subject: Re: SMP on FreeBSD 6.x and 7.0: Worth doing? Message-ID: <200712241549.IAA19650@lariat.net> In-Reply-To: <476FBED0.2080400@samsco.org> References: <200712220531.WAA09277@lariat.net> <476FBED0.2080400@samsco.org>
next in thread | previous in thread | raw e-mail | index | archive | help
At 07:14 AM 12/24/2007, Scott Long wrote: >Brett, > >There could be several problems here: > >1. WITNESS, INVARIANTS, malloc debugging. Are any of these turned on for you? I don't recall if malloc debugging got turned off yet for the >7.0 snapshots. I nuked debugging when I recompiled the kernel with SCHED_ULE. >2. Disk subsystem. What kind of disk controller are you using? Not all >drivers work well in FreeBSD. Are linux and freebsd using identical >hardware? They were. The drives are SATA. >3. Directory hashing. If you're using squid, you __must__ tune the DIRHASH, otherwise you'll spend a lot of time doing pathname lookups. What filesystem is linux using? Whatever comes standard with Ubuntu. As for directory hashing: Squid doesn't use more than 256 entries in each one, so that's what I normally set. I also normally do a newfs with parameters that favor the distribution of object sizes found in Web caches. (We did this on both Linux and FreeBSD.) >Would you mind if I logged into your test system and looked around to >help diagnose the problem? The system isn't online now, because it's been a week since the tests and I also wanted to try the 6.3 beta and a few hardware changes. My guess, based on what I saw, is that UFS2 doesn't take as much advantage of SMP as Linux's file system does and threads are blocking on file I/O. (Networking does not seem to be the botteneck, though I have heard that the IP stack in 7-CURRENT needs optimization and that this had been proposed as a sponsored project.) --Brett P.S. -- If the chip manufacturers were not making it so that one needs to go to SMP to get more processing power, I wouldn't be doing SMP. I'd rather use FreeBSD 4.11 on a single core "gaming" CPU, as I did a few years ago when I needed a very fast server. But this isn't a viable option nowadays....
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200712241549.IAA19650>