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=-15.7 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable 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 C8272C388F9 for ; Thu, 19 Nov 2020 23:28:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5E7DE22227 for ; Thu, 19 Nov 2020 23:28:20 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="jLyRdwi8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727217AbgKSX2A (ORCPT ); Thu, 19 Nov 2020 18:28:00 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34140 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726123AbgKSX15 (ORCPT ); Thu, 19 Nov 2020 18:27:57 -0500 Received: from mail-ej1-x641.google.com (mail-ej1-x641.google.com [IPv6:2a00:1450:4864:20::641]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id BF33BC0613CF; Thu, 19 Nov 2020 15:27:56 -0800 (PST) Received: by mail-ej1-x641.google.com with SMTP id i19so10313667ejx.9; Thu, 19 Nov 2020 15:27:56 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=vG0la9jq/M1aNuNVjI3CB3YTuTYiHqFptMWAHHu2/GY=; b=jLyRdwi89tUGez6ZXP1Zywcgv/TYl9a3cfj3c82Sur0K7xQFtnLPahePEpIYWZDVdF 7kvhQAGbvUH17EwLsLHkIZZFl0BGshnpbFpvKVJkNRq2X1aeikzGVMRhcPABOdxdMGpx TzCJ94gKzQqJ3B1FBH8wCMAQkDkOW5itOgxtv/NjfOBzzM7SBE9NvKbI9e7g2GnRyHrN 95l3s4xCF8TWXAOoC/ZYStJ5sXeiw41DXYWTQvoKj9IIjYB56ePcXTw/FaIqsHwBAFjp YYctGqoBLXIs4wOAqrnyRWDxMPhWkXs+g55kmStCfqOt3jsWP4b3amGodWCJTJb0TD// yG9g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=vG0la9jq/M1aNuNVjI3CB3YTuTYiHqFptMWAHHu2/GY=; b=MtMdY9427WIioUBm4ozazEJKhcnLN/5FkF9PJRuoFdENIaWEyuZYt1SXhz/u5blNAw OIe3LKh7UteWshh9ty7HAR45pWu9cEdOAcvcJESWk5920ija1sQpI4TKy25wfBAofO4h RpVe1vAtRLno8Yt2LcdL7ZJQ9g4KFgwJKcsIJ4qrpmcHITVWaYFLyjxTwL84ram/YAYu Wu3fmQ14jYCgOCYo45feqL0L7AXH3n4otTxCxxa8T17LktiC6RzaNztxwqloIBlwNhQP 3pz7Bf89q7QII4WVg4v8EE5cKfhezq2a6rFy69/M3eEp/sGoN3QUT7JhMfhpv/u+J2/6 IpKw== X-Gm-Message-State: AOAM531zevsaea3rxDO0J3aP+v2FxUOlFlQHcLGd06UuCB0ryaMSqox4 M0INettBwsVRrhvPq6n0dndtKKbHApMQZQ== X-Google-Smtp-Source: ABdhPJymWkJd80yAzlT02yp+AoXi45G9dWs64mgBWGw9Jv3MS5mr+duBUJXA8o5Mvk37jtI/ITmgxA== X-Received: by 2002:a17:906:a195:: with SMTP id s21mr29337444ejy.146.1605828474887; Thu, 19 Nov 2020 15:27:54 -0800 (PST) Received: from localhost.localdomain (host109-152-100-135.range109-152.btcentralplus.com. [109.152.100.135]) by smtp.gmail.com with ESMTPSA id n3sm458114ejl.33.2020.11.19.15.27.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Nov 2020 15:27:54 -0800 (PST) From: Pavel Begunkov To: linux-fsdevel@vger.kernel.org, Alexander Viro Cc: Jens Axboe , linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v2 1/2] iov_iter: optimise iov_iter_npages for bvec Date: Thu, 19 Nov 2020 23:24:38 +0000 Message-Id: X-Mailer: git-send-email 2.24.0 In-Reply-To: References: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The block layer spends quite a while in iov_iter_npages(), but for the bvec case the number of pages is already known and stored in iter->nr_segs, so it can be returned immediately as an optimisation Perf for an io_uring benchmark with registered buffers (i.e. bvec) shows ~1.5-2.0% total cycle count spent in iov_iter_npages(), that's dropped by this patch to ~0.2%. Reviewed-by: Jens Axboe Signed-off-by: Pavel Begunkov --- lib/iov_iter.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 1635111c5bd2..0fa7ac330acf 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1594,6 +1594,8 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) return 0; if (unlikely(iov_iter_is_discard(i))) return 0; + if (unlikely(iov_iter_is_bvec(i))) + return min_t(int, i->nr_segs, maxpages); if (unlikely(iov_iter_is_pipe(i))) { struct pipe_inode_info *pipe = i->pipe; @@ -1614,11 +1616,9 @@ int iov_iter_npages(const struct iov_iter *i, int maxpages) - p / PAGE_SIZE; if (npages >= maxpages) return maxpages; - 0;}),({ - npages++; - if (npages >= maxpages) - return maxpages; - }),({ + 0;}), + 0 /* bvecs are handled above */ + ,({ unsigned long p = (unsigned long)v.iov_base; npages += DIV_ROUND_UP(p + v.iov_len, PAGE_SIZE) - p / PAGE_SIZE; -- 2.24.0