Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755406Ab2ENJI0 (ORCPT ); Mon, 14 May 2012 05:08:26 -0400 Received: from mail-lpp01m010-f46.google.com ([209.85.215.46]:55416 "EHLO mail-lpp01m010-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755375Ab2ENJIY (ORCPT ); Mon, 14 May 2012 05:08:24 -0400 MIME-Version: 1.0 In-Reply-To: <201205140859.52921.arnd@arndb.de> References: <201205101049.58818.arnd@arndb.de> <201205140859.52921.arnd@arndb.de> Date: Mon, 14 May 2012 11:08:22 +0200 Message-ID: Subject: Re: Big I/O latencies, except when iotop is hooked From: Felipe Contreras To: Arnd Bergmann Cc: Linux Kernel Mailing List Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2009 Lines: 54 Hi, On Mon, May 14, 2012 at 10:59 AM, Arnd Bergmann wrote: > On Thursday 10 May 2012, Arnd Bergmann wrote: >> 176 is extremely bad, yes. A good value would be between 1 and 3. >> The algorithm is probably not 'la' but 'dl' and the page size (-b) >> could be smaller -- you have to test by passing '--blocksize=1024' to >> the --open-au test and see where it starts getting drastically >> smaller (if 4KB gives you about half the throughput of 8KB, >> 8KB is the page size). Those two can make the result better. >> >> As I said, the erase block size is more likely to be 4MB, which >> will make the flashsim result worse. >> >> Does flashsim give a better number for a trace taken with iotop >> running? >> >> Can you send me or upload that iolog file? > > Hi Felipe, > > Any update? Nope, sorry, my laptop got fried. I have a new one and I might be able to test later today, I don't see why I would have any problems reproducing this there, but lets see. > I'd really be interested in the trace file so that we > can look at data of a real-world case that hurts. I've discussed > your problem in the Linaro storage team meeting, and the question > came up whether this only happens with encryption enabled. As I already said, this also happens without encryption. > Which kind of encryption method do you actually use? Depending > on how the encryption is implemented, two things could possibly > go wrong that would not happen without it: I just do 'cryptsetup luksFormat' I'm not sure what is their default. According to the manpage it's aes-cbc-essiv:sha256. I tried with different --align-payload values, but none that actually improved the situation. Anyway, the problem is visible even with plain ext4. Cheers. -- Felipe Contreras -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/