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=-8.5 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, 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 5D3D1C04EB9 for ; Mon, 3 Dec 2018 22:05:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id F27A120851 for ; Mon, 3 Dec 2018 22:05:20 +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="jBejBUsu" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F27A120851 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 S1725933AbeLCWFU (ORCPT ); Mon, 3 Dec 2018 17:05:20 -0500 Received: from mail-pl1-f179.google.com ([209.85.214.179]:35635 "EHLO mail-pl1-f179.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725848AbeLCWFU (ORCPT ); Mon, 3 Dec 2018 17:05:20 -0500 Received: by mail-pl1-f179.google.com with SMTP id p8so7174699plo.2 for ; Mon, 03 Dec 2018 14:05:19 -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=Hj7I4GeFND7vrkQ8VTy4myM76ZlT7HGPXBAMplE4OOc=; b=jBejBUsu5qZHAFv//Rix7yXFnpmcJ7pwTwAs7i8J3DEofqhxDL/aI55sb0Skf/2BPo 9Yll+Uwngx4p/othWTtZ6rp2oEP33SWluY3vnSiQ7KLIWSfgFyJudWmoVXTsBt/TUbR4 pctKxSXVMfony4+fIRmjsfmDcteSFj2mkQ5ZsRF9Bw04HM5ZDcy7vt0U1YPwSn2XuNQO tbaiEE08dM0PXJX2oa9N+yAuj4tv8QWZ5wdUtKwM4dzIw1G1VN2xVIcifeuOfNsILjJ4 sZf8L13fsCuTyKqkdESVSz/Q4AExaKmAcemJbfZRlVesdvpU2wpujF7+yYwBMl/dC83m GeCg== 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=Hj7I4GeFND7vrkQ8VTy4myM76ZlT7HGPXBAMplE4OOc=; b=HRotLY+CyoPgGHM5hb9sCUHgLYHPPfyZJDUf8CR2mh0ItLsCqv12Jhe/vlHhKEUQBI JbfGMwsKE63nQBMtjWaIYZH3OjuRyHrlicHBA5Kr+rf8WNTbs7PyiHLNDVoR4CN+7F2o J6vVC/pHSKDkrn8MZa+JOf4uQGYRrvz8N+uGCSAozpUgtif0iqiOi2FlkQ49r9BPk+z3 U2zCZNpq0XvuOifmFuN+Imd1ydcHdq8DEO5K3VmaZ/QYIrxIahCKOIWDW6bPU/nOjnuR 2DDqt62slhHYIsGh3sQW4+BZitnfNCxtrUpq1FhDwQSX/mBngqbiw5B0XH/SOxQhtp8E 4JbA== X-Gm-Message-State: AA+aEWY2VfMSh8/1uFzYEY9T5juO8cd1rPMSSlzB7SvggvjM9+vpva1t B0rVUJCGj03XjFmbuFUWZwarDA== X-Google-Smtp-Source: AFSGD/XvFqOfHW/vOacknN0aRhxksAsvO56EiWA81is5h2Xy4K1dDWAoNNYvknUvB8Vebbm3DXzLkg== X-Received: by 2002:a17:902:bcc7:: with SMTP id o7mr17961405pls.281.1543874718886; Mon, 03 Dec 2018 14:05:18 -0800 (PST) Received: from vader ([2620:10d:c090:200::5:8421]) by smtp.gmail.com with ESMTPSA id z8sm31389651pgz.53.2018.12.03.14.05.18 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 03 Dec 2018 14:05:18 -0800 (PST) Date: Mon, 3 Dec 2018 14:05:17 -0800 From: Omar Sandoval To: Jens Axboe Cc: "linux-block@vger.kernel.org" Subject: Re: sbitmap: check cleared bits when iterating busy bits Message-ID: <20181203220517.GD11220@vader> References: <8bde3953-56d8-32cb-2c34-582d632f4a3f@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8bde3953-56d8-32cb-2c34-582d632f4a3f@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 Mon, Dec 03, 2018 at 02:56:17PM -0700, Jens Axboe wrote: > When we are iterating the set bits in a word, we also need to factor in > the cleared bits. Don't call fn() unless the bit is also not set in > the cleared word. > > Fixes: ea86ea2cdced ("sbitmap: ammortize cost of clearing bits") > Signed-off-by: Jens Axboe > > diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h > index 92806a2dbab7..9f374fbcdba6 100644 > --- a/include/linux/sbitmap.h > +++ b/include/linux/sbitmap.h > @@ -283,6 +283,11 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb, > nr = find_next_bit(&word->word, depth, nr); > if (nr >= depth) > break; > + /* if set in cleared, it's actually free */ > + if (test_bit(nr, &word->cleared)) { > + nr++; > + continue; > + } > if (!fn(sb, (index << sb->shift) + nr, data)) > return; > > -- > Jens Axboe > How about something like this: diff --git a/include/linux/sbitmap.h b/include/linux/sbitmap.h index f0f49bbb2617..fe9122386255 100644 --- a/include/linux/sbitmap.h +++ b/include/linux/sbitmap.h @@ -265,12 +265,14 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb, nr = SB_NR_TO_BIT(sb, start); while (scanned < sb->depth) { - struct sbitmap_word *word = &sb->map[index]; - unsigned int depth = min_t(unsigned int, word->depth - nr, + unsigned long word; + unsigned int depth = min_t(unsigned int, + sb->map[index].depth - nr, sb->depth - scanned); scanned += depth; - if (!word->word) + word = sb->map[index].word & ~sb->map[index].cleared; + if (!word) goto next; /* @@ -280,7 +282,7 @@ static inline void __sbitmap_for_each_set(struct sbitmap *sb, */ depth += nr; while (1) { - nr = find_next_bit(&word->word, depth, nr); + nr = find_next_bit(&word, depth, nr); if (nr >= depth) break; if (!fn(sb, (index << sb->shift) + nr, data)) Might be marginally faster.