From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ua0-f198.google.com (mail-ua0-f198.google.com [209.85.217.198]) by kanga.kvack.org (Postfix) with ESMTP id 359956B02FA for ; Wed, 31 May 2017 15:02:48 -0400 (EDT) Received: by mail-ua0-f198.google.com with SMTP id 23so665036uaj.5 for ; Wed, 31 May 2017 12:02:48 -0700 (PDT) Received: from mail-ua0-x233.google.com (mail-ua0-x233.google.com. [2607:f8b0:400c:c08::233]) by mx.google.com with ESMTPS id g2si8080397uah.81.2017.05.31.12.02.46 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 31 May 2017 12:02:47 -0700 (PDT) Received: by mail-ua0-x233.google.com with SMTP id u10so15049321uaf.1 for ; Wed, 31 May 2017 12:02:46 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <87h9014j7t.fsf@concordia.ellerman.id.au> From: Mathieu Malaterre Date: Wed, 31 May 2017 21:02:25 +0200 Message-ID: Subject: Re: 4.12-rc ppc64 4k-page needs costly allocations Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Hugh Dickins Cc: Christoph Lameter , linuxppc-dev , "Aneesh Kumar K.V" , linux-mm@kvack.org On Wed, May 31, 2017 at 8:44 PM, Hugh Dickins wrote: > [ Merging two mails into one response ] > > On Wed, 31 May 2017, Christoph Lameter wrote: >> On Tue, 30 May 2017, Hugh Dickins wrote: >> > SLUB: Unable to allocate memory on node -1, gfp=0x14000c0(GFP_KERNEL) >> > cache: pgtable-2^12, object size: 32768, buffer size: 65536, default order: 4, min order: 4 >> > pgtable-2^12 debugging increased min order, use slub_debug=O to disable. >> >> > I did try booting with slub_debug=O as the message suggested, but that >> > made no difference: it still hoped for but failed on order:4 allocations. >> >> I am curious as to what is going on there. Do you have the output from >> these failed allocations? > > I thought the relevant output was in my mail. I did skip the Mem-Info > dump, since that just seemed noise in this case: we know memory can get > fragmented. What more output are you looking for? > >> >> > I wanted to try removing CONFIG_SLUB_DEBUG, but didn't succeed in that: >> > it seemed to be a hard requirement for something, but I didn't find what. >> >> CONFIG_SLUB_DEBUG does not enable debugging. It only includes the code to >> be able to enable it at runtime. > > Yes, I thought so. > >> >> > I did try CONFIG_SLAB=y instead of SLUB: that lowers these allocations to >> > the expected order:3, which then results in OOM-killing rather than direct >> > allocation failure, because of the PAGE_ALLOC_COSTLY_ORDER 3 cutoff. But >> > makes no real difference to the outcome: swapping loads still abort early. >> >> SLAB uses order 3 and SLUB order 4??? That needs to be tracked down. >> >> Ahh. Ok debugging increased the object size to an order 4. This should be >> order 3 without debugging. > > But it was still order 4 when booted with slub_debug=O, which surprised me. > And that surprises you too? If so, then we ought to dig into it further. > >> >> Why are the slab allocators used to create slab caches for large object >> sizes? > > There may be more optimal ways to allocate, but I expect that when > the ppc guys are writing the code to handle both 4k and 64k page sizes, > kmem caches offer the best span of possibility without complication. > >> >> > Relying on order:3 or order:4 allocations is just too optimistic: ppc64 >> > with 4k pages would do better not to expect to support a 128TB userspace. >> >> I thought you had these huge 64k page sizes? > > ppc64 does support 64k page sizes, and they've been the default for years; > but since 4k pages are still supported, I choose to use those (I doubt > I could ever get the same load going with 64k pages). 4k is pretty much required on ppc64 when it comes to nouveau: https://bugs.freedesktop.org/show_bug.cgi?id=94757 2cts -- 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