Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751528AbaAYGJ3 (ORCPT ); Sat, 25 Jan 2014 01:09:29 -0500 Received: from mail-pd0-f174.google.com ([209.85.192.174]:46542 "EHLO mail-pd0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751095AbaAYGJ0 convert rfc822-to-8bit (ORCPT ); Sat, 25 Jan 2014 01:09:26 -0500 References: <1377186876-57291-1-git-send-email-tmac@hp.com> <1390588288-66930-1-git-send-email-tmac@hp.com> <87fvodcb65.fsf@tassilo.jf.intel.com> Mime-Version: 1.0 (1.0) In-Reply-To: <87fvodcb65.fsf@tassilo.jf.intel.com> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8BIT Message-Id: Cc: T Makphaibulchoke , "viro@zeniv.linux.org.uk" , "tytso@mit.edu" , "adilger.kernel@dilger.ca" , "linux-ext4@vger.kernel.org" , "linux-kernel@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "aswin@hp.com" X-Mailer: iPhone Mail (11B554a) From: Andreas Dilger Subject: Re: [PATCH v4 0/3] ext4: increase mbcache scalability Date: Fri, 24 Jan 2014 23:09:24 -0700 To: Andi Kleen Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org I think the ext4 block groups are locked with the blockgroup_lock that has about the same number of locks as the number of cores, with a max of 128, IIRC. See blockgroup_lock.h. While there is some chance of contention, it is also unlikely that all of the cores are locking this area at the same time. Cheers, Andreas > On Jan 24, 2014, at 14:38, Andi Kleen wrote: > > T Makphaibulchoke writes: > >> The patch consists of three parts. >> >> The first part changes the implementation of both the block and hash chains of >> an mb_cache from list_head to hlist_bl_head and also introduces new members, >> including a spinlock to mb_cache_entry, as required by the second part. > > spinlock per entry is usually overkill for larger hash tables. > > Can you use a second smaller lock table that just has locks and is > indexed by a subset of the hash key. Most likely a very small > table is good enough. > > Also I would be good to have some data on the additional memory consumption. > > -Andi > > -- > ak@linux.intel.com -- Speaking for myself only -- 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/