From: Andrew Morton Subject: Re: [PATCH 1/2] ext2: speed up file creates by optimizing rec_len functions Date: Tue, 7 Dec 2010 13:07:08 -0800 Message-ID: <20101207130708.71c894e9.akpm@linux-foundation.org> References: <4CFE7347.8030807@redhat.com> <4CFE7409.9090609@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: ext4 development , Jan Kara To: Eric Sandeen Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:52495 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754134Ab0LGVHo (ORCPT ); Tue, 7 Dec 2010 16:07:44 -0500 In-Reply-To: <4CFE7409.9090609@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, 07 Dec 2010 11:51:05 -0600 Eric Sandeen wrote: > The addition of 64k block capability in the rec_len_from_disk > and rec_len_to_disk functions added a bit of math overhead which > slows down file create workloads needlessly when the architecture > cannot even support 64k blocks, thanks to page size limits. > > The directory entry checking can also be optimized a bit > by sprinkling in some unlikely() conditions to move the > error handling out of line. > > bonnie++ sequential file creates on a 512MB ramdisk speeds up > from about 2200/s to about 2500/s, about a 14% improvement. > hrm, that's an improbably-large sounding improvement from eliminating just a few test-n-branches from a pretty heavyweight operation.