From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-10.5 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SIGNED_OFF_BY,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 28C2DC04EB9 for ; Thu, 29 Nov 2018 21:57:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id C3F9321019 for ; Thu, 29 Nov 2018 21:57:53 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org C3F9321019 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726362AbeK3JEq (ORCPT ); Fri, 30 Nov 2018 04:04:46 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55004 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726344AbeK3JEp (ORCPT ); Fri, 30 Nov 2018 04:04:45 -0500 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id CD6576EB87; Thu, 29 Nov 2018 21:57:52 +0000 (UTC) Received: from localhost (unknown [10.18.25.149]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 67DBA19743; Thu, 29 Nov 2018 21:57:47 +0000 (UTC) Date: Thu, 29 Nov 2018 16:57:47 -0500 From: Mike Snitzer To: Mikulas Patocka Cc: Jens Axboe , dm-devel@redhat.com, linux-block@vger.kernel.org, "Alasdair G. Kergon" , Christoph Hellwig Subject: Re: [PATCH 2/3] block: switch to per-cpu in-flight counters Message-ID: <20181129215746.GA9226@redhat.com> References: <20181128004250.325095242@debian.vm> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181128004250.325095242@debian.vm> User-Agent: Mutt/1.5.21 (2010-09-15) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Thu, 29 Nov 2018 21:57:52 +0000 (UTC) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Tue, Nov 27 2018 at 7:42pm -0500, Mikulas Patocka wrote: > Now when part_round_stats is gone, we can switch to per-cpu in-flight > counters. > > We use the local-atomic type local_t, so that if part_inc_in_flight or > part_dec_in_flight is reentrantly called from an interrupt, the value will > be correct. > > The other counters could be corrupted due to reentrant interrupt, but the > corruption only results in slight counter skew - the in_flight counter > must be exact, so it needs local_t. > > Signed-off-by: Mikulas Patocka > > --- > block/bio.c | 4 ++-- > block/blk-core.c | 4 ++-- > block/blk-merge.c | 2 +- > block/genhd.c | 47 +++++++++++++++++++++++++++++++++++------------ > drivers/md/dm.c | 4 +--- > include/linux/genhd.h | 7 ++++--- > 6 files changed, 45 insertions(+), 23 deletions(-) > ... > Index: linux-block/drivers/md/dm.c > =================================================================== > --- linux-block.orig/drivers/md/dm.c 2018-11-28 00:09:59.000000000 +0100 > +++ linux-block/drivers/md/dm.c 2018-11-28 00:09:59.000000000 +0100 > @@ -663,8 +663,7 @@ static void start_io_acct(struct dm_io * > generic_start_io_acct(md->queue, bio_op(bio), bio_sectors(bio), > &dm_disk(md)->part0); > > - atomic_set(&dm_disk(md)->part0.in_flight[rw], > - atomic_inc_return(&md->pending[rw])); > + atomic_inc(&md->pending[rw]); > > if (unlikely(dm_stats_used(&md->stats))) > dm_stats_account_io(&md->stats, bio_data_dir(bio), > @@ -693,7 +692,6 @@ static void end_io_acct(struct dm_io *io > * a flush. > */ > pending = atomic_dec_return(&md->pending[rw]); > - atomic_set(&dm_disk(md)->part0.in_flight[rw], pending); > pending += atomic_read(&md->pending[rw^0x1]); > > /* nudge anyone waiting on suspend queue */ > These dm.c hunks conflict with changes from you that I already staged in dm-4.21, see: https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.21&id=b5616f7a11592cc74860f4ec3e3c4fba6688eefa https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/commit/?h=dm-4.21&id=78f95b53c203c969bbe6b86e405f7a891a43b6be I'd really like to get away from DM maintaining its own ->pending counters. Mike