Date: Sat, 08 Jan 2005 20:13:16 -0600 From: Ryan Sommers <ryans@gamersimpact.com> To: David Malone <dwmalone@maths.tcd.ie> Cc: freebsd-hackers@freebsd.org Subject: Re: Benchmark: NetBSD 2.0 beats FreeBSD 5.3 Message-ID: <41E0933C.9010405@gamersimpact.com> In-Reply-To: <20050108202605.GA30807@walton.maths.tcd.ie> References: <41DE4F3D.8050509@syskonnect.de> <20050107091004.83732.qmail@web52710.mail.yahoo.com> <20050107101006.GA2553@frontfree.net> <20050108135526.GQ49329@submonkey.net> <Pine.OSX.4.61.0501081320080.603@oof.local> <20050108202605.GA30807@walton.maths.tcd.ie>
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David Malone wrote: >On Sat, Jan 08, 2005 at 01:21:14PM -0500, Charles Sprickman wrote: > > >>Any idea what type of impact this patch would have on say, a large qmail >>server that's drowning in context-switches? >> >> > >It will depend on how many processes you have running at any one >moment and how often processes are created/destroyed. From the look >of the graphs, you won't really be able to tell unless there are >significantly more than 1000 processes running at any moment. > > David. > > This could be the case. It's my understanding that Qmail spawns a new qmail-local process (specifically qmail-lspawn exec's it) for each locally delivered message. For any remote message qmail-rspawn forks a qmail-remote process. I don't believe these processes live longer than a single instance. Depending on how his mailboxes are setup this can even result in new processes being spawned. If you're running vpopmail qmail-local will pipe the message to vdelivermail. And if you're running anything like spamassassin from vpopmail (as opposed to from qmail via the QMAIL_QUEUE patch, although that will spawn a spamc of it's own) this could result in another executed process (spamc is spamd's light-weight front-end). Depending on how large and busy this qmail server is, there could definately be a large amount of time spent in process creation and teardown. I'm not sure how much Charles is familiar with the Qmail+vpopmail+spamassassin, if he is using spamassassin. But, one of the "hidden" features of using SpamAssassin and Vpopmail as installed from ports is that spamassassin is called from vpopmail. There is no run-time option (only compile time that is defaulted to on) to disable this. A lot of users don't realize this and will use the QMAIL_QUEUE patch and run spamassassin from it. This can result in scanning every email twice, which can be a costly oversight. -- Ryan Sommers ryans@gamersimpact.com
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