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Date: Mon, 9 Apr 2007 19:30:56 -0700 From: Andrew Morton <akpm@...ux-foundation.org> To: Dave Jones <davej@...hat.com> Cc: Jeff Garzik <jeff@...zik.org>, Robin Holt <holt@....com>, "Eric W. Biederman" <ebiederm@...ssion.com>, Ingo Molnar <mingo@...e.hu>, Linus Torvalds <torvalds@...ux-foundation.org>, linux-kernel@...r.kernel.org, Jack Steiner <steiner@...ricas.sgi.com> Subject: Re: init's children list is long and slows reaping children. On Mon, 9 Apr 2007 21:59:12 -0400 Dave Jones <davej@...hat.com> wrote: > On Mon, Apr 09, 2007 at 05:23:39PM -0700, Andrew Morton wrote: > > > I suspect there are quite a few kernel threads which don't really need to > > be threads at all: the code would quite happily work if it was changed to > > use keventd, via schedule_work() and friends. But kernel threads are > > somewhat easier to code for. > > Perhaps too easy. We have a bunch of kthreads sitting around that afaict, > are there 'just in case', not because they're actually in use. This is fun. > 10 ? S< 0:00 [khelper] That one's needed to parent the call_usermodehelper() apps. I don't think it does anything else. We used to use keventd for this but that had some problem whcih I forget. (Who went and misnamed keventd to "events", too? Nobody calls it "events", and with good reason) > Why doesn't this get spawned when it needs to? > > 164 ? S< 0:00 [cqueue/0] > 165 ? S< 0:00 [cqueue/1] > > I'm not even sure wth these are. Me either. > ... > : root 3 0.0 0.0 0 0 ? S 18:51 0:00 [watchdog/0] That's the softlockup detector. Confusingly named to look like a, err, watchdog. Could probably use keventd. : root 5 0.0 0.0 0 0 ? S 18:51 0:00 [khelper] That's there to parent the kthread_create()d threads. Could presumably use khelper. : root 152 0.0 0.0 0 0 ? S 18:51 0:00 [ata/0] Does it need to be per-cpu? : root 153 0.0 0.0 0 0 ? S 18:51 0:00 [ata_aux] That's a single-threaded workqueue handler. Perhaps could use keventd. : root 299 0.0 0.0 0 0 ? S 18:51 0:00 [scsi_eh_0] : root 300 0.0 0.0 0 0 ? S 18:51 0:00 [scsi_eh_1] : root 305 0.0 0.0 0 0 ? S 18:51 0:00 [scsi_eh_2] : root 306 0.0 0.0 0 0 ? S 18:51 0:00 [scsi_eh_3] This machine has one CPU, one sata disk and one DVD drive. The above is hard to explain. : root 319 0.0 0.0 0 0 ? S 18:51 0:00 [pccardd] hm. : root 331 0.0 0.0 0 0 ? S 18:51 0:00 [kpsmoused] hm. : root 337 0.0 0.0 0 0 ? S 18:51 0:00 [kedac] hm. I didn't know that the Vaio had EDAC. : root 1173 0.0 0.0 0 0 ? S 18:51 0:00 [khpsbpkt] I can't even pronounce that. : root 1354 0.0 0.0 0 0 ? S 18:51 0:00 [knodemgrd_0] OK, I do have 1394 hardware, but it hasn't been used. : root 1636 0.0 0.0 0 0 ? S 18:52 0:00 [kondemand/0] I blame davej. > > otoh, a lot of these inefficeincies are probably down in scruffy drivers > > rather than in core or top-level code. > > You say scruffy, but most of the proliferation of kthreads comes > from code written in the last few years. Compare the explosion of kthreads > we see coming from 2.4 to 2.6. It's disturbing, and I don't see it > slowing down at all. > > On the 2-way box I grabbed the above ps output from, I end up with 69 kthreads. > It doesn't surprise me at all that bigger iron is starting to see issues. > Sure. I don't think it's completely silly to object to all this. Sure, a kernel thread is worth 4k in the best case, but I bet they have associated unused resources and as we've seen, they can cause overhead. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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