Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752242AbaFDKed (ORCPT ); Wed, 4 Jun 2014 06:34:33 -0400 Received: from mx1.redhat.com ([209.132.183.28]:46018 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751927AbaFDKec (ORCPT ); Wed, 4 Jun 2014 06:34:32 -0400 Date: Wed, 4 Jun 2014 12:35:45 +0200 From: Alexander Gordeev To: Jens Axboe Cc: linux-kernel@vger.kernel.org, Ming Lei Subject: blk-mq: bitmap tag: performance degradation? Message-ID: <20140604103544.GA11350@dhcp-26-207.brq.redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Jens, et al With new bitmap tags I am observing performance degradation on 'null_blk' device with 512 queue depth. This is 'fio' config used: [global] bs=4k size=16g [nullb] filename=/dev/nullb0 direct=1 rw=randread numjobs=8 I tried machines with 16 and 48 CPUs and it seems the more CPUs we have the worse the result. Here is 48 CPUs one: 3.15.0-rc4+ READ: io=131072MB, aggrb=3128.7MB/s, minb=400391KB/s, maxb=407204KB/s, mint=41201msec, maxt=41902msec 548,549,235,428 cycles:k 3,759,335,303 L1-dcache-load-misses 419,021,008 cache-misses:k 39.659121371 seconds time elapsed 3.15.0-rc1.for-3.16-blk-mq-tagging+ READ: io=131072MB, aggrb=1951.8MB/s, minb=249824KB/s, maxb=255851KB/s, mint=65574msec, maxt=67156msec 1,063,669,976,651 cycles:k 4,572,746,591 L1-dcache-load-misses 1,127,037,813 cache-misses:k 69.446112553 seconds time elapsed Thanks! -- Regards, Alexander Gordeev agordeev@redhat.com -- 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/