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=-5.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,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 D1F1CC04EB8 for ; Fri, 30 Nov 2018 21:37:53 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8E1EA20663 for ; Fri, 30 Nov 2018 21:37:53 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=osandov-com.20150623.gappssmtp.com header.i=@osandov-com.20150623.gappssmtp.com header.b="Y9WUV0Wo" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E1EA20663 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=osandov.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 S1726078AbeLAIsc (ORCPT ); Sat, 1 Dec 2018 03:48:32 -0500 Received: from mail-pg1-f195.google.com ([209.85.215.195]:36196 "EHLO mail-pg1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725941AbeLAIsb (ORCPT ); Sat, 1 Dec 2018 03:48:31 -0500 Received: by mail-pg1-f195.google.com with SMTP id n2so3048433pgm.3 for ; Fri, 30 Nov 2018 13:37:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=osandov-com.20150623.gappssmtp.com; s=20150623; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=3tuak7JnyZqKp/ecO2KsIkyJPmUmmZ4op+2SAsKmhEo=; b=Y9WUV0WogEcE7qpi+v+OD55ZIMK7hNcD5nyD2XuqGP7dmz7lZrOhveS1EGEQdYcyzR Mp4WP9VyZGwH5ezUtu9k//CiOvwJ6wQocepZllkLRF/5X5crKmNJ+6guRHLHy+yXRdpX 8Mubiyifca2CZHen8948LWvy1URwoueOEcrFQ+21DW6HENRCf/NSt/mlVgxbJSRJl+M7 wFEv8bDmHL4Jx7jgk/HEfSBCofiPtRif4FWxofg664WQ1RdE/z3rLn/Q8gryekTlQ5FF IaDma9tZF4RsVV9qs2zRJ5ryr9wArF1DuCuFIpIHq3wbgLEn+ZJx4VCTET4Jqq/zChu0 EJCg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=3tuak7JnyZqKp/ecO2KsIkyJPmUmmZ4op+2SAsKmhEo=; b=Z1plNMO9+uneL/QbXyI92aNogl6GWf/knzpkTOPJ7rnGYfyJQvy4+pCJdlZaO+O3+V XzpqO8uzPccDHiB/6BzJMFM+nGGsVJVDsEOBh6gIw83Xel1EQ4hS+pVaREOET93tq+Gz DZjCmhQXqW+FP/pekGzkAPRJYFevln/YuektJRwOQ1NXCn3iSJNSUQjF+2IwEZxrdzXf qmbYU5s6fD/8fVdHdzXCs7JEY+iDSEL1FeAHqRTOiAQpe1vm+8F6eMfWRS2Ufz4NSg+6 0bAcqj6z5FT0S7RU/BhXxCehLJSYPehdrFiZtG2wzsDWANEZ8qwqGv3eJv4BNvsOxfPd ENCg== X-Gm-Message-State: AA+aEWZ33WeU/ZFyBqE6NVIkxy1M2izCUxasZL7K2ko2wAbORTwGhZof 8/10UJ4ujUZRmzkHweVhSErylg== X-Google-Smtp-Source: AFSGD/VXjktjTCTBBVfohW9QkkT2zMb6YS4mzcfK17iDBwZTZBFlLipITvwN/k/ZDH2NKkF1ackH8w== X-Received: by 2002:a62:670f:: with SMTP id b15mr7169928pfc.212.1543613871830; Fri, 30 Nov 2018 13:37:51 -0800 (PST) Received: from vader ([2620:10d:c090:200::4:705d]) by smtp.gmail.com with ESMTPSA id a16-v6sm7876755pfh.107.2018.11.30.13.37.50 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Fri, 30 Nov 2018 13:37:51 -0800 (PST) Date: Fri, 30 Nov 2018 13:37:50 -0800 From: Omar Sandoval To: Jens Axboe Cc: linux-block@vger.kernel.org Subject: Re: [PATCH 2/2] sbitmap: optimize wakeup check Message-ID: <20181130213750.GA11220@vader> References: <20181130160118.24683-1-axboe@kernel.dk> <20181130160118.24683-3-axboe@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181130160118.24683-3-axboe@kernel.dk> User-Agent: Mutt/1.11.0 (2018-11-25) Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Fri, Nov 30, 2018 at 09:01:18AM -0700, Jens Axboe wrote: > Even if we have no waiters on any of the sbitmap_queue wait states, we > still have to loop every entry to check. We do this for every IO, so > the cost adds up. > > Shift a bit of the cost to the slow path, when we actually have waiters. > Wrap prepare_to_wait_exclusive() and finish_wait(), so we can maintain > an internal count of how many are currently active. Then we can simply > check this count in sbq_wake_ptr() and not have to loop if we don't > have any sleepers. > > Convert the two users of sbitmap with waiting, blk-mq-tag and iSCSI. Reviewed-by: Omar Sandoval > Signed-off-by: Jens Axboe > --- > block/blk-mq-tag.c | 11 ++++---- > drivers/target/iscsi/iscsi_target_util.c | 12 +++++---- > include/linux/sbitmap.h | 34 ++++++++++++++++++++++++ > lib/sbitmap.c | 28 +++++++++++++++++++ > 4 files changed, 74 insertions(+), 11 deletions(-)