From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ted Ts'o Subject: Re: Any qualms about reverting 3d0518f4, ext4: New rec_len encoding for very large blocksizes ? Date: Tue, 3 Aug 2010 19:12:19 -0400 Message-ID: <20100803231219.GH9453@thunk.org> References: <4C58987B.2040602@redhat.com> <38BC6435-5556-422C-BFA3-A964F6C6E6B9@dilger.ca> <4C589CF2.9030406@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Andreas Dilger , ext4 development , Wei Yongjun To: Eric Sandeen Return-path: Received: from thunk.org ([69.25.196.29]:48447 "EHLO thunker.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756417Ab0HCXMU (ORCPT ); Tue, 3 Aug 2010 19:12:20 -0400 Content-Disposition: inline In-Reply-To: <4C589CF2.9030406@redhat.com> Sender: linux-ext4-owner@vger.kernel.org List-ID: On Tue, Aug 03, 2010 at 05:49:22PM -0500, Eric Sandeen wrote: > > As far as I know, reverting it won't break 64kb dir blocks...? I seem to recall there was some confusion about what was the correct way of recording a rec_len of 64k --- 0 or 65535. So after reverting the patch, we need to make sure we didn't end up breaking compatibility with (a) existing file systems and (b) what older versions of mke2fs may have generated. > >> (this does 200 iterations) and got this for the file creations: > >> > >> ext4 stock: Average = 21206.8 files/s > >> ext4 patched: Average = 22822.1 files/s > >> > >> This is a 7.6% improvement... Wow. I assume that was because actually ending up burning enough CPU time that it slowed bonnie's performance? I'm not sure how how realistic is a benchmark that is simply creating vast numbers of small files in a tight loop, but certainly on non-Itanium systems where the page size is nowhere near 64k, it's arguably pointless. (Can you even configure an Itanic to have to have a page size > 64k?) So one way of dealing wih this is making it an inline, and then #ifdef'ing out the more complex code if the page size is < 64k.... - Ted