From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [RFC][PATCH] lru_add_drain_all() don't use schedule_on_each_cpu() From: Peter Zijlstra In-Reply-To: <20081027120405.1B45.KOSAKI.MOTOHIRO@jp.fujitsu.com> References: <2f11576a0810260851h15cb7e1ahb454b70a2e99e1a8@mail.gmail.com> <1225037872.32713.22.camel@twins> <20081027120405.1B45.KOSAKI.MOTOHIRO@jp.fujitsu.com> Content-Type: text/plain Content-Transfer-Encoding: 7bit Date: Mon, 27 Oct 2008 08:56:30 +0100 Message-Id: <1225094190.16159.3.camel@twins> Mime-Version: 1.0 Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: Heiko Carstens , Nick Piggin , linux-kernel@vger.kernel.org, Hugh Dickins , Andrew Morton , Linus Torvalds , Rik van Riel , Lee Schermerhorn , linux-mm@kvack.org, Christoph Lameter , Gautham Shenoy , Oleg Nesterov , Rusty Russell , mpm List-ID: On Mon, 2008-10-27 at 12:14 +0900, KOSAKI Motohiro wrote: > > Right, and would be about 4k+sizeof(task_struct), some people might be > > bothered, but most won't care. > > > > > Perhaps, I misunderstand your intension. so can you point your > > > previous discussion url? > > > > my google skillz fail me, but once in a while people complain that we > > have too many kernel threads. > > > > Anyway, if we can re-use this per-cpu workqueue for more goals, I guess > > there is even less of an objection. > > In general, you are right. > but this is special case. mmap_sem is really widely used various subsystem and drivers. > (because page fault via copy_user introduce to depend on mmap_sem) > > Then, any work-queue reu-sing can cause similar dead-lock easily. Yeah, I know, and the cpu-hotplug discussion needed another thread due to yet another locking incident. I was hoping these two could go together. Neither are general-purpose workqueues, both need to stay away from the normal eventd due to deadlocks. ego, does you extra thread ever use mmap_sem? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org