From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752039AbbEJV4M (ORCPT ); Sun, 10 May 2015 17:56:12 -0400 Received: from imap.thunk.org ([74.207.234.97]:55738 "EHLO imap.thunk.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751582AbbEJV4L (ORCPT ); Sun, 10 May 2015 17:56:11 -0400 Date: Sun, 10 May 2015 17:56:07 -0400 From: "Theodore Ts'o" To: Bernhard Kraft Cc: linux-kernel@vger.kernel.org Subject: Re: ext2/3/4 performance issue Message-ID: <20150510215607.GA14298@thunk.org> Mail-Followup-To: Theodore Ts'o , Bernhard Kraft , linux-kernel@vger.kernel.org References: <554F1045.4070105@think-open.at> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <554F1045.4070105@think-open.at> User-Agent: Mutt/1.5.23 (2014-03-12) X-SA-Exim-Connect-IP: X-SA-Exim-Mail-From: tytso@thunk.org X-SA-Exim-Scanned: No (on imap.thunk.org); SAEximRunCond expanded to false Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, May 10, 2015 at 10:01:09AM +0200, Bernhard Kraft wrote: > > I work on implementing the ext2 filesystem for a PIC microcontroller and > while reading the sources of it in the linux kernel I stumbled upon the > following performance issue..... Your observations are currect as far as ext2 is concerned; by the time you get to ext4, it's a bit more complicated. Also, the extN_bg_has_super() has in general not been a bottleneck, at least on modern CPUs. Perhaps it would be more of an issue on a PIC microcontroller, of course. Finally, note that the overhead is cached so it is only calculated the first time the extN_statfs() is called. Cheers, - Ted