Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752539AbbEFBV2 (ORCPT ); Tue, 5 May 2015 21:21:28 -0400 Received: from g4t3426.houston.hp.com ([15.201.208.54]:55790 "EHLO g4t3426.houston.hp.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752156AbbEFBVX (ORCPT ); Tue, 5 May 2015 21:21:23 -0400 Message-ID: <55496C8F.606@hp.com> Date: Tue, 05 May 2015 21:21:19 -0400 From: Waiman Long User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.12) Gecko/20130109 Thunderbird/10.0.12 MIME-Version: 1.0 To: Andrew Morton CC: Mel Gorman , Nathan Zimmer , Dave Hansen , Scott Norton , Daniel J Blueman , Linux-MM , LKML Subject: Re: [PATCH 0/13] Parallel struct page initialisation v4 References: <1430231830-7702-1-git-send-email-mgorman@suse.de> <554030D1.8080509@hp.com> <5543F802.9090504@hp.com> <554415B1.2050702@hp.com> <20150504143046.9404c572486caf71bdef0676@linux-foundation.org> <20150505104514.GC2462@suse.de> <20150505130255.49ff76bbf0a3b32d884ab2ce@linux-foundation.org> In-Reply-To: <20150505130255.49ff76bbf0a3b32d884ab2ce@linux-foundation.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2279 Lines: 49 On 05/05/2015 04:02 PM, Andrew Morton wrote: > On Tue, 5 May 2015 11:45:14 +0100 Mel Gorman wrote: > >> On Mon, May 04, 2015 at 02:30:46PM -0700, Andrew Morton wrote: >>>> Before the patch, the boot time from elilo prompt to ssh login was 694s. >>>> After the patch, the boot up time was 346s, a saving of 348s (about 50%). >>> Having to guesstimate the amount of memory which is needed for a >>> successful boot will be painful. Any number we choose will be wrong >>> 99% of the time. >>> >>> If the kswapd threads have started, all we need to do is to wait: take >>> a little nap in the allocator's page==NULL slowpath. >>> >>> I'm not seeing any reason why we can't start kswapd much earlier - >>> right at the start of do_basic_setup()? >> It doesn't even have to be kswapd, it just should be a thread pinned to >> a done. The difficulty is that dealing with the system hashes means the >> initialisation has to happen before vfs_caches_init_early() when there is >> no scheduler. > I bet we can run vfs_caches_init_early() after sched_init(). Might > need a few little fixups. > >> Those allocations could be delayed further but then there is >> the possibility that the allocations would not be contiguous and they'd >> have to rely on CMA to make the attempt. That potentially alters the >> performance of the large system hashes at run time. > hm, why. If the kswapd threads are running and busily creating free > pages then alloc_pages(order=10) can detect this situation and stall > for a while, waiting for kswapd to create an order-10 page. > > Alternatively, the page allocator can go off and synchronously > initialize some pageframes itself. Keep doing that until the > allocation attempt succeeds. > > Such an approach is much more robust than trying to predict how much > memory will be needed. > Most of those hash tables are allocated before smp_boot. In UP mode, you can't have another thread initializing memory. So we really need to preallocate enough for those tables. Cheers, Longman -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/