From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx111.postini.com [74.125.245.111]) by kanga.kvack.org (Postfix) with SMTP id 5F0BA6B002B for ; Wed, 17 Oct 2012 15:13:41 -0400 (EDT) Received: by mail-ea0-f169.google.com with SMTP id k11so2181345eaa.14 for ; Wed, 17 Oct 2012 12:13:39 -0700 (PDT) Subject: Re: [Q] Default SLAB allocator From: Eric Dumazet In-Reply-To: <507EFCC3.1050304@am.sony.com> References: <1350392160.3954.986.camel@edumazet-glaptop> <507DA245.9050709@am.sony.com> <1350414968.3954.1427.camel@edumazet-glaptop> <507EFCC3.1050304@am.sony.com> Content-Type: text/plain; charset="UTF-8" Date: Wed, 17 Oct 2012 21:13:37 +0200 Message-ID: <1350501217.26103.852.camel@edumazet-glaptop> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Tim Bird Cc: Ezequiel Garcia , David Rientjes , Andi Kleen , Linux Kernel Mailing List , "linux-mm@kvack.org" , "celinux-dev@lists.celinuxforum.org" On Wed, 2012-10-17 at 11:45 -0700, Tim Bird wrote: > 8G is a small web server? The RAM budget for Linux on one of > Sony's cameras was 10M. We're not merely not in the same ballpark - > you're in a ballpark and I'm trimming bonsai trees... :-) > Even laptops in 2012 have +4GB of ram. (Maybe not Sony laptops, I have to double check ?) Yes, servers do have more ram than laptops. (Maybe not Sony servers, I have to double check ?) > > # 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. > In this example, it appears that if all kmalloc-8's were pushed into 32-byte slabs, > we'd lose about 1.8 meg due to pure slab overhead. This would not be noise > on my system. I said : 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 I think your 10M cameras are very tiny hosts. Using SLUB on them might not be the best choice. First time I ran linux, years ago, it was on 486SX machines with 8M of memory (or maybe less, I dont remember exactly). But I no longer use this class of machines with recent kernels. # size vmlinux text data bss dec hex filename 10290631 1278976 1896448 13466055 cd79c7 vmlinux -- 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