From mboxrd@z Thu Jan 1 00:00:00 1970 Subject: Re: [PATCH -mm 17/25] Mlocked Pages are non-reclaimable From: Lee Schermerhorn In-Reply-To: <20080610171400.149886cf@cuia.bos.redhat.com> References: <20080606202838.390050172@redhat.com> <20080606202859.522708682@redhat.com> <20080606180746.6c2b5288.akpm@linux-foundation.org> <20080610033130.GK19404@wotan.suse.de> <20080610171400.149886cf@cuia.bos.redhat.com> Content-Type: text/plain Date: Tue, 10 Jun 2008 17:43:17 -0400 Message-Id: <1213134197.6872.49.camel@lts-notebook> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Rik van Riel Cc: Nick Piggin , Andrew Morton , linux-kernel@vger.kernel.org, kosaki.motohiro@jp.fujitsu.com, linux-mm@kvack.org, eric.whitney@hp.com List-ID: On Tue, 2008-06-10 at 17:14 -0400, Rik van Riel wrote: > On Tue, 10 Jun 2008 05:31:30 +0200 > Nick Piggin wrote: > > > If we eventually run out of page flags on 32 bit, then sure this might be > > one we could look at geting rid of. Once the code has proven itself. > > Yes, after the code has proven stable, we can probably get > rid of the PG_mlocked bit and use only PG_unevictable to mark > these pages. > > Lee, Kosaki-san, do you see any problem with that approach? > Is the PG_mlocked bit really necessary for non-debugging > purposes? > Well, it does speed up the check for mlocked pages in page_reclaimable() [now page_evictable()?] as we don't have to walk the reverse map to determine that a page is mlocked. In many places where we currently test page_reclaimable(), we really don't want to and maybe can't walk the reverse map. Unless you're evisioning even larger rework, the PG_unevictable flag [formerly PG_noreclaim, right?] is analogous to PG_active. It's only set when the page is on the corresponding lru list or being held isolated from it, temporarily. See isolate_lru_page() and putback_lru_page() and users thereof--such as mlock_vma_page(). Again, I have seen what changes you're making here, so maybe that's all changing. But, currently, PG_unevictable would not be a replacement for PG_mlocked. Anyway, let's see what you come up with before we tackle this. Couple of related items: + 26-rc5-mm1 + a small fix to the double unlock_page() in shrink_page_list() has been running for a couple of hours on my 32G, 16cpu ia64 numa platform w/o error. Seems to have survived the merge into -mm, despite the issues Andrew has raised. + on same platform, Mel Gorman's mminit debug code is reporting that we're using 22 page flags with Noreclaim, Mlock and PAGEFLAGS_EXTENDED configured. Lee -- 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