Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753488Ab2JMMoE (ORCPT ); Sat, 13 Oct 2012 08:44:04 -0400 Received: from mail-ie0-f174.google.com ([209.85.223.174]:36242 "EHLO mail-ie0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753390Ab2JMMoC (ORCPT ); Sat, 13 Oct 2012 08:44:02 -0400 MIME-Version: 1.0 In-Reply-To: References: Date: Sat, 13 Oct 2012 09:44:01 -0300 Message-ID: Subject: Re: [Q] Default SLAB allocator From: Ezequiel Garcia To: David Rientjes Cc: Andi Kleen , Linux Kernel Mailing List , linux-mm@kvack.org, Tim Bird , celinux-dev@lists.celinuxforum.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1733 Lines: 53 Hi David, On Sat, Oct 13, 2012 at 6:54 AM, David Rientjes wrote: > On Fri, 12 Oct 2012, Ezequiel Garcia wrote: > >> >> SLUB is a non-starter for us and incurs a >10% performance degradation in >> >> netperf TCP_RR. >> > >> >> Where are you seeing that? >> > > In my benchmarking results. > >> Notice that many defconfigs are for embedded devices, >> and many of them say "use SLAB"; I wonder if that's right. >> > > If a device doesn't require the smallest memory footprint possible (SLOB) > then SLAB is the right choice when there's a limited amount of memory; > SLUB requires higher order pages for the best performance (on my desktop > system running with CONFIG_SLUB, over 50% of the slab caches default to be > high order). > But SLAB suffers from a lot more internal fragmentation than SLUB, which I guess is a known fact. So memory-constrained devices would waste more memory by using SLAB. I must admit a didn't look at page order (but I will now). >> Is there any intention to replace SLAB by SLUB? > > There may be an intent, but it'll be nacked as long as there's a > performance degradation. > >> In that case it could make sense to change defconfigs, although >> it wouldn't be based on any actual tests. >> > > Um, you can't just go changing defconfigs without doing some due diligence > in ensuring it won't be deterimental for those users. Yeah, it would be very interesting to compare SLABs on at least some of those platforms. Ezequiel -- 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/