From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx145.postini.com [74.125.245.145]) by kanga.kvack.org (Postfix) with SMTP id 12CAC6B002B for ; Tue, 16 Oct 2012 14:02:53 -0400 (EDT) Message-ID: <507DA245.9050709@am.sony.com> Date: Tue, 16 Oct 2012 11:07:01 -0700 From: Tim Bird MIME-Version: 1.0 Subject: Re: [Q] Default SLAB allocator References: <1350392160.3954.986.camel@edumazet-glaptop> In-Reply-To: <1350392160.3954.986.camel@edumazet-glaptop> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Eric Dumazet Cc: Ezequiel Garcia , David Rientjes , Andi Kleen , Linux Kernel Mailing List , "linux-mm@kvack.org" , "celinux-dev@lists.celinuxforum.org" On 10/16/2012 05:56 AM, Eric Dumazet wrote: > On Tue, 2012-10-16 at 09:35 -0300, Ezequiel Garcia wrote: > >> Now, returning to the fragmentation. The problem with SLAB is that >> its smaller cache available for kmalloced objects is 32 bytes; >> while SLUB allows 8, 16, 24 ... >> >> Perhaps adding smaller caches to SLAB might make sense? >> Is there any strong reason for NOT doing this? > > I would remove small kmalloc-XX caches, as sharing a cache line > is sometime dangerous for performance, because of false sharing. > > They make sense only for very small hosts. That's interesting... It would be good to measure the performance/size tradeoff here. I'm interested in very small systems, and it might be worth the tradeoff, depending on how bad the performance is. Maybe a new config option would be useful (I can hear the groans now... :-) Ezequiel - do you have any measurements of how much memory is wasted by 32-byte kmalloc allocations for smaller objects, in the tests you've been doing? -- Tim ============================= Tim Bird Architecture Group Chair, CE Workgroup of the Linux Foundation Senior Staff Engineer, Sony Network Entertainment ============================= -- 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