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=-8.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT 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 5AA04C282DD for ; Sat, 20 Apr 2019 16:36:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 2483A20869 for ; Sat, 20 Apr 2019 16:36:42 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=zoho.com header.i=yehs2007@zoho.com header.b="q+F51iBM" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728474AbfDTQgk (ORCPT ); Sat, 20 Apr 2019 12:36:40 -0400 Received: from sender4-pp-o95.zoho.com ([136.143.188.95]:25575 "EHLO sender4-pp-o95.zoho.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725920AbfDTQgk (ORCPT ); Sat, 20 Apr 2019 12:36:40 -0400 X-Greylist: delayed 960 seconds by postgrey-1.27 at vger.kernel.org; Sat, 20 Apr 2019 12:36:40 EDT ARC-Seal: i=1; a=rsa-sha256; t=1555777291; cv=none; d=zoho.com; s=zohoarc; b=HTTiHkVrcGhltWl5YAo3q2rbVhPtA+0GwwyrLHmS4VKvbq5ttxag2hORUZDVMu770xfDR+RGrZXHdg0Pp3ImGJK9NR031Ly+iwEnivHTazfRPo12DLzKx1vW4cuq4pAenOi/KH7Ew9C19GVtfVTGKT8Dgt1ggDz48wqnkzR1W5c= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=zoho.com; s=zohoarc; t=1555777291; h=Cc:Date:From:Message-ID:Subject:To:ARC-Authentication-Results; bh=TcNyGdTYH8VgNNRiNbi3oWrA2PtCg8NXMlUiWnytha0=; b=PEmN+q9K4LM7Q/XG7Rkm/sP29MWTua0jE++uz5Eww5MmcfQQcpDiyMQhKTnnzEQdCLY8MNvNe3PtWwkqdh88f+C0xr32XAFvUhwMmAUGrNa/G/9zRxzAdBotf7scSMT9rSpqd8XC77dzoAFPj64tsvGFmB1a+h9AGnl7YB7sAGM= ARC-Authentication-Results: i=1; mx.zoho.com; dkim=pass header.i=zoho.com; spf=pass smtp.mailfrom=yehs2007@zoho.com; dmarc=pass header.from= header.from= DomainKey-Signature: a=rsa-sha1; q=dns; c=nofws; s=zapps768; d=zoho.com; h=from:to:cc:subject:date:message-id; b=WP02vy0FtGpNKokpfMAsYa6Ujnvi41sehSzVQf/d1S6m3ddvyp0xgyyWwnCGaKPeyBWShjr1czte XbUObcvp0lc+gMvPgpbBqiP9OJSKxq+htM7iG1mE8Kx44pE2ecXl DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; t=1555777291; s=default; d=zoho.com; i=yehs2007@zoho.com; h=From:To:Cc:Subject:Date:Message-Id; l=1759; bh=TcNyGdTYH8VgNNRiNbi3oWrA2PtCg8NXMlUiWnytha0=; b=q+F51iBMBHlKziRuq/HKKUsY6n1sYwPc97acF2fIHRa/f5haNObTpazWlAyguWwv YxOiUvYh4q7zD4rCUm2ky+TFHEU+mPQOedsF7cc9AvnYlRCudj9o30WMQOm0fz6U+Oe NVKr5lPr293WaEOuwWtlrh/GoE7NknR+cRq1Wot0= Received: from YEHS1XR3054QMS.lenovo.com (123.118.182.142 [123.118.182.142]) by mx.zohomail.com with SMTPS id 1555777290062966.0734097869595; Sat, 20 Apr 2019 09:21:30 -0700 (PDT) From: Huaisheng Ye To: mpatocka@redhat.com, snitzer@redhat.com, agk@redhat.com Cc: prarit@redhat.com, chengnt@lenovo.com, dm-devel@redhat.com, linux-kernel@vger.kernel.org, Huaisheng Ye Subject: [PATCH] dm-writecache: avoid unnecessary lookups in writecache_find_entry Date: Sun, 21 Apr 2019 00:21:02 +0800 Message-Id: <20190420162102.6460-1-yehs2007@zoho.com> X-Mailer: git-send-email 2.17.0.windows.1 X-ZohoMailClient: External Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Huaisheng Ye Only when entry has been found, that would only be necessary to check the lowest or highest seq-count. Add local variable "found" in writecache_find_entry, if no entry has been found, it is meaningless that having a useless rb_prev or rb_next. Signed-off-by: Huaisheng Ye --- drivers/md/dm-writecache.c | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/drivers/md/dm-writecache.c b/drivers/md/dm-writecache.c index ddf1732..047ae09 100644 --- a/drivers/md/dm-writecache.c +++ b/drivers/md/dm-writecache.c @@ -537,14 +537,18 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc, { struct wc_entry *e; struct rb_node *node = wc->tree.rb_node; + bool found = false; if (unlikely(!node)) return NULL; while (1) { e = container_of(node, struct wc_entry, rb_node); - if (read_original_sector(wc, e) == block) + if (read_original_sector(wc, e) == block) { + found = true; break; + } + node = (read_original_sector(wc, e) >= block ? e->rb_node.rb_left : e->rb_node.rb_right); if (unlikely(!node)) { @@ -564,7 +568,8 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc, } } - while (1) { + /* only need to check lowest or highest seq-count when entry has been found */ + while (found) { struct wc_entry *e2; if (flags & WFE_LOWEST_SEQ) node = rb_prev(&e->rb_node); @@ -577,6 +582,9 @@ static struct wc_entry *writecache_find_entry(struct dm_writecache *wc, return e; e = e2; } + + /* no entry has been found, return the following entry */ + return e; } static void writecache_insert_entry(struct dm_writecache *wc, struct wc_entry *ins) -- 1.8.3.1