From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752693Ab0KHPjs (ORCPT ); Mon, 8 Nov 2010 10:39:48 -0500 Received: from mx1.redhat.com ([209.132.183.28]:1027 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752450Ab0KHPjr (ORCPT ); Mon, 8 Nov 2010 10:39:47 -0500 From: Jeff Moyer To: Dave Chinner Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/3] dio: scale unaligned IO tracking via multiple lists References: <1289202023-15102-1-git-send-email-david@fromorbit.com> <1289202023-15102-3-git-send-email-david@fromorbit.com> X-PGP-KeyID: 1F78E1B4 X-PGP-CertKey: F6FE 280D 8293 F72C 65FD 5A58 1FF8 A7CA 1F78 E1B4 X-PCLoadLetter: What the f**k does that mean? Date: Mon, 08 Nov 2010 10:36:06 -0500 In-Reply-To: <1289202023-15102-3-git-send-email-david@fromorbit.com> (Dave Chinner's message of "Mon, 8 Nov 2010 18:40:22 +1100") Message-ID: User-Agent: Gnus/5.110011 (No Gnus v0.11) Emacs/23.1 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Dave Chinner writes: > From: Dave Chinner > > To avoid concerns that a single list and lock tracking the unaligned > IOs will not scale appropriately, create multiple lists and locks > and chose them by hashing the unaligned block being zeroed. > > Signed-off-by: Dave Chinner > --- > fs/direct-io.c | 49 ++++++++++++++++++++++++++++++++++++------------- > 1 files changed, 36 insertions(+), 13 deletions(-) > > diff --git a/fs/direct-io.c b/fs/direct-io.c > index 1a69efd..353ac52 100644 > --- a/fs/direct-io.c > +++ b/fs/direct-io.c > @@ -152,8 +152,28 @@ struct dio_zero_block { > atomic_t ref; /* reference count */ > }; > > -static DEFINE_SPINLOCK(dio_zero_block_lock); > -static LIST_HEAD(dio_zero_block_list); > +#define DIO_ZERO_BLOCK_NR 37LL I'm always curious to know how these numbers are derived. Why 37? Cheers, Jeff