From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f70.google.com (mail-pg0-f70.google.com [74.125.83.70]) by kanga.kvack.org (Postfix) with ESMTP id 9CDDD6B025F for ; Thu, 5 Oct 2017 04:39:36 -0400 (EDT) Received: by mail-pg0-f70.google.com with SMTP id a192so2467206pge.5 for ; Thu, 05 Oct 2017 01:39:36 -0700 (PDT) Received: from mx1.suse.de (mx2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id j5si4460616pgt.437.2017.10.05.01.39.35 for (version=TLS1 cipher=AES128-SHA bits=128/128); Thu, 05 Oct 2017 01:39:35 -0700 (PDT) Date: Thu, 5 Oct 2017 10:39:33 +0200 From: Jan Kara Subject: Re: [PATCH] mm: readahead: Increase maximum readahead window Message-ID: <20171005083933.GB28132@quack2.suse.cz> References: <20171004091205.468-1-jack@suse.cz> <20171004174151.GA6497@magnolia> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20171004174151.GA6497@magnolia> Sender: owner-linux-mm@kvack.org List-ID: To: "Darrick J. Wong" Cc: Jan Kara , Andrew Morton , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org On Wed 04-10-17 10:41:51, Darrick J. Wong wrote: > On Wed, Oct 04, 2017 at 11:12:05AM +0200, Jan Kara wrote: > > Increase default maximum allowed readahead window from 128 KB to 512 KB. > > This improves performance for some workloads (see below for details) where > > ability to scale readahead window to larger sizes allows for better total > > throughput while chances for regression are rather low given readahead > > window size is dynamically computed based on observation (and thus it never > > grows large for workloads with a random read pattern). > > > > Note that the same tuning can be done using udev rules or by manually setting > > the sysctl parameter however we believe the new value is a better default most > > users will want to use. As a data point we carry this patch in SUSE kernels > > for over 8 years. > > > > Some data from the last evaluation of this patch (on 4.4-based kernel, I can > > rerun those tests on a newer kernel but nothing has changed in the readahead > > area since 4.4). The patch was evaluated on two machines > > This is purely speculating, but I think this is worth at least a quick > retry on 4.14 to see what's changed in the past 10 kernel release. For > one thing, ext3 no longer exists, and XFS' file IO path has changed > quite a lot since then. ext3 in this test is actually using ext4 driver already, so that has not changed. I agree XFS has changed quite a bit so results might differ there. I can rerun it with current kernel to see whether XFS behavior changed. Honza -- Jan Kara SUSE Labs, CR -- 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