From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f46.google.com (mail-pa0-f46.google.com [209.85.220.46]) by kanga.kvack.org (Postfix) with ESMTP id 95EA76B0035 for ; Tue, 26 Aug 2014 17:22:10 -0400 (EDT) Received: by mail-pa0-f46.google.com with SMTP id lj1so24082587pab.5 for ; Tue, 26 Aug 2014 14:22:10 -0700 (PDT) Received: from qmta14.emeryville.ca.mail.comcast.net (qmta14.emeryville.ca.mail.comcast.net. [2001:558:fe2d:44:76:96:27:212]) by mx.google.com with ESMTP id gy2si6148819pbb.106.2014.08.26.14.22.09 for ; Tue, 26 Aug 2014 14:22:09 -0700 (PDT) Date: Tue, 26 Aug 2014 16:22:06 -0500 (CDT) From: Christoph Lameter Subject: Re: [PATCH 1/3] mm/slab: use percpu allocator for cpu cache In-Reply-To: <20140826021904.GA1035@js1304-P5Q-DELUXE> Message-ID: References: <1408608675-20420-1-git-send-email-iamjoonsoo.kim@lge.com> <20140825082615.GA13475@js1304-P5Q-DELUXE> <20140826021904.GA1035@js1304-P5Q-DELUXE> Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Joonsoo Kim Cc: Andrew Morton , Pekka Enberg , David Rientjes , linux-mm@kvack.org, Tejun Heo , linux-kernel@vger.kernel.org On Tue, 26 Aug 2014, Joonsoo Kim wrote: > > What case? SLUB uses a linked list and therefore does not have these > > storage requirements. > > I misunderstand that you mentioned just memory usage. My *any case* > means memory usage of previous SLAB and SLAB with this percpu alloc > change. Sorry for confusion. Ok. True the total amount of memory used does not increase. > > > I know that percpu allocator occupy vmalloc space, so maybe we could > > > exhaust vmalloc space on 32 bit. 64 bit has no problem on it. > > > How many cores does largest 32 bit system have? Is it possible > > > to exhaust vmalloc space if we use percpu allocator? > > > > There were NUMA systems on x86 a while back (not sure if they still > > exists) with 128 or so processors. > > > > Some people boot 32 bit kernels on contemporary servers. The Intel ones > > max out at 18 cores (36 hyperthreaded). I think they support up to 8 > > scokets. So 8 * 36? > > > > > > Its different on other platforms with much higher numbers. Power can > > easily go up to hundreds of hardware threads and SGI Altixes 7 yearsago > > where at 8000 or so. > > Okay... These large systems with 32 bit kernel could be break with this > change. I will do more investigation. Possibly, I will drop this patch. :) Wait the last system mentioned are 64 bit. SGI definitely. Power probably too. -- 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