Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755982Ab2JPTQQ (ORCPT ); Tue, 16 Oct 2012 15:16:16 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:51660 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755838Ab2JPTQM (ORCPT ); Tue, 16 Oct 2012 15:16:12 -0400 Subject: Re: [Q] Default SLAB allocator From: Eric Dumazet To: Ezequiel Garcia Cc: Tim Bird , David Rientjes , Andi Kleen , Linux Kernel Mailing List , "linux-mm@kvack.org" , "celinux-dev@lists.celinuxforum.org" In-Reply-To: References: <1350392160.3954.986.camel@edumazet-glaptop> <507DA245.9050709@am.sony.com> Content-Type: text/plain; charset="UTF-8" Date: Tue, 16 Oct 2012 21:16:08 +0200 Message-ID: <1350414968.3954.1427.camel@edumazet-glaptop> Mime-Version: 1.0 X-Mailer: Evolution 2.28.3 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1716 Lines: 46 On Tue, 2012-10-16 at 15:27 -0300, Ezequiel Garcia wrote: > Yes, we have some numbers: > > http://elinux.org/Kernel_dynamic_memory_analysis#Kmalloc_objects > > Are they too informal? I can add some details... > > They've been measured on a **very** minimal setup, almost every option > is stripped out, except from initramfs, sysfs, and trace. > > On this scenario, strings allocated for file names and directories > created by sysfs > are quite noticeable, being 4-16 bytes, and produce a lot of fragmentation from > that 32 byte cache at SLAB. > > Is an option to enable small caches on SLUB and SLAB worth it? Random small web server : # free total used free shared buffers cached Mem: 7884536 5412572 2471964 0 155440 1803340 -/+ buffers/cache: 3453792 4430744 Swap: 2438140 51164 2386976 # grep Slab /proc/meminfo Slab: 351592 kB # egrep "kmalloc-32|kmalloc-16|kmalloc-8" /proc/slabinfo kmalloc-32 11332 12544 32 128 1 : tunables 0 0 0 : slabdata 98 98 0 kmalloc-16 5888 5888 16 256 1 : tunables 0 0 0 : slabdata 23 23 0 kmalloc-8 76563 82432 8 512 1 : tunables 0 0 0 : slabdata 161 161 0 Really, some waste on these small objects is pure noise on SMP hosts. (Waste on bigger objects is probably more important by orders of magnitude) -- 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/