From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx158.postini.com [74.125.245.158]) by kanga.kvack.org (Postfix) with SMTP id E813B6B0032 for ; Wed, 17 Jul 2013 01:18:00 -0400 (EDT) Received: by mail-oa0-f46.google.com with SMTP id h1so1958090oag.33 for ; Tue, 16 Jul 2013 22:18:00 -0700 (PDT) Message-ID: <51E628F8.6030303@gmail.com> Date: Wed, 17 Jul 2013 13:17:44 +0800 From: Sam Ben MIME-Version: 1.0 Subject: Re: [RFC 0/4] Transparent on-demand struct page initialization embedded in the buddy allocator References: <1373594635-131067-1-git-send-email-holt@sgi.com> In-Reply-To: <1373594635-131067-1-git-send-email-holt@sgi.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Robin Holt Cc: "H. Peter Anvin" , Ingo Molnar , Nate Zimmer , Linux Kernel , Linux MM , Rob Landley , Mike Travis , Daniel J Blueman , Andrew Morton , Greg KH , Yinghai Lu , Mel Gorman On 07/12/2013 10:03 AM, Robin Holt wrote: > We have been working on this since we returned from shutdown and have > something to discuss now. We restricted ourselves to 2MiB initialization > to keep the patch set a little smaller and more clear. > > First, I think I want to propose getting rid of the page flag. If I knew > of a concrete way to determine that the page has not been initialized, > this patch series would look different. If there is no definitive > way to determine that the struct page has been initialized aside from > checking the entire page struct is zero, then I think I would suggest > we change the page flag to indicate the page has been initialized. > > The heart of the problem as I see it comes from expand(). We nearly > always see a first reference to a struct page which is in the middle > of the 2MiB region. Due to that access, the unlikely() check that was > originally proposed really ends up referencing a different page entirely. > We actually did not introduce an unlikely and refactor the patches to > make that unlikely inside a static inline function. Also, given the > strong warning at the head of expand(), we did not feel experienced > enough to refactor it to make things always reference the 2MiB page > first. > > With this patch, we did boot a 16TiB machine. Without the patches, > the v3.10 kernel with the same configuration took 407 seconds for > free_all_bootmem. With the patches and operating on 2MiB pages instead > of 1GiB, it took 26 seconds so performance was improved. I have no feel > for how the 1GiB chunk size will perform. How to test how much time spend on free_all_bootmem? > > I am on vacation for the next three days so I am sorry in advance for > my infrequent or non-existant responses. > > > Signed-off-by: Robin Holt > Signed-off-by: Nate Zimmer > To: "H. Peter Anvin" > To: Ingo Molnar > Cc: Linux Kernel > Cc: Linux MM > Cc: Rob Landley > Cc: Mike Travis > Cc: Daniel J Blueman > Cc: Andrew Morton > Cc: Greg KH > Cc: Yinghai Lu > Cc: Mel Gorman > -- > 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/ -- 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