From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 52B066B022E for ; Fri, 30 Apr 2010 16:53:25 -0400 (EDT) Date: Fri, 30 Apr 2010 13:52:39 -0700 From: Andrew Morton Subject: Re: [PATCH] - New round-robin rotor for SLAB allocations Message-Id: <20100430135239.7782f6ba.akpm@linux-foundation.org> In-Reply-To: <20100426210041.GA6580@sgi.com> References: <20100426210041.GA6580@sgi.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Jack Steiner Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, cl@linux-foundation.org, Pekka Enberg List-ID: On Mon, 26 Apr 2010 16:00:41 -0500 Jack Steiner wrote: > We have observed several workloads running on multi-node systems where > memory is assigned unevenly across the nodes in the system. There are > numerous reasons for this but one is the round-robin rotor in > cpuset_mem_spread_node(). > > For example, a simple test that writes a multi-page file will allocate pages > on nodes 0 2 4 6 ... Odd nodes are skipped. (Sometimes it allocates on > odd nodes & skips even nodes). > > An example is shown below. The program "lfile" writes a file consisting of > 10 pages. The program then mmaps the file & uses get_mempolicy(..., > MPOL_F_NODE) to determine the nodes where the file pages were allocated. > The output is shown below: > > # ./lfile > allocated on nodes: 2 4 6 0 1 2 6 0 2 > > > > There is a single rotor that is used for allocating both file pages & slab > pages. Writing the file allocates both a data page & a slab page > (buffer_head). This advances the RR rotor 2 nodes for each page > allocated. > > A quick confirmation seems to confirm this is the cause of the uneven > allocation: > > # echo 0 >/dev/cpuset/memory_spread_slab > # ./lfile > allocated on nodes: 6 7 8 9 0 1 2 3 4 5 > > > This patch introduces a second rotor that is used for slab allocations. > > include/linux/cpuset.h | 6 ++++++ > include/linux/sched.h | 1 + > kernel/cpuset.c | 20 ++++++++++++++++---- > mm/slab.c | 2 +- > 4 files changed, 24 insertions(+), 5 deletions(-) Why no update to slob and slub? -- 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