From nobody Tue Apr 7 17:32:56 2026 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 92124C433FE for ; Tue, 18 Oct 2022 14:52:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231489AbiJROwe (ORCPT ); Tue, 18 Oct 2022 10:52:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41970 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230366AbiJROwQ (ORCPT ); Tue, 18 Oct 2022 10:52:16 -0400 Received: from mail-ed1-x52e.google.com (mail-ed1-x52e.google.com [IPv6:2a00:1450:4864:20::52e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A44E7D994F; Tue, 18 Oct 2022 07:52:11 -0700 (PDT) Received: by mail-ed1-x52e.google.com with SMTP id q19so20817024edd.10; Tue, 18 Oct 2022 07:52:11 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc:subject:date:message-id:reply-to; bh=VdDndPV91SgyMkTQ4AOZFrCVVQ8EFi+AlwFk89m7OCk=; b=jwtBcSs6qlzBVVm91NsjwcTCP82c4aIoxUossafUf6XaZ2aVFUsQcqfvzeYwmUNdEa 5jBy455pdXEKITguIhHME9Rp+sMEXzqwaIa4YydgLm45obZvK1SJfajY4o4gFcXkQNwy wl0Boi6R9GqyvJ9Rf7wEz53UC+9Yah51GgptczMSH9f7o0DGX8aQN4Ffvq0zc1BYa0x0 QgM8qx9+buDMSmJ1TUetY3v/J4yLMOIQBBrq6sQAV7fHJZ3j+lMchRDWZA6EWBdZ1W/C HCSQEvhZMqqMNFhO8OhhxlR/Gg/tHfPfFDk9OwoYcFeuDWriKsoZ9odzgftCCRv05ssB 8YIA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=VdDndPV91SgyMkTQ4AOZFrCVVQ8EFi+AlwFk89m7OCk=; b=MCZ7Kh5cBhnl78mKz/dhF6O8EQ3JG+/W4ZssBbXjRMU+gopO4N13p2+TBeKh88hQaP g258FuOahn864Rv3ElzvbvWRZnQl/Ccuux5zLxGEC9Peb23MCyJ0CWGUXQ0wuschl4No kvxicGptY/I6pbbOkKwvOlx4xVa7FgGu9qIqaMpz4wDMo4/XMLQK1lH4Eq/Nvawv+B2T rt7b3fIVEA9Xus3HxOyuZ8x7CL55i3PfI9vabYkoB7FO0ogGizsbzR+n8Ol2ZCOaLyRf zYYHk2RWSK+M+SlHo1TEQ+GPeEVLLLf28SJ4yhFZgdhboEV59tR3SxyPGYnMrQAUFepc g4PA== X-Gm-Message-State: ACrzQf2yoEPSNLszYyEoA5rbb/Ad35Ldmc0Lw+WNnwIlZh5zw6ttfgbO bnE3fW+V2ks5JbTLzc3W7MZSJ8kVKhv7PA== X-Google-Smtp-Source: AMsMyM4nlHReoog0AoDXBjeuOIWhgm+BBc6vmW4PoHknsNjVcIkvHFcirWG7Yt2b6HMWAjQN4AhdZg== X-Received: by 2002:a05:6402:c7:b0:457:cd5d:d777 with SMTP id i7-20020a05640200c700b00457cd5dd777mr2891686edu.245.1666104729452; Tue, 18 Oct 2022 07:52:09 -0700 (PDT) Received: from localhost.localdomain ([46.248.82.114]) by smtp.gmail.com with ESMTPSA id l2-20020a056402028200b0045bd14e241csm9033063edv.76.2022.10.18.07.52.08 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 18 Oct 2022 07:52:08 -0700 (PDT) From: Uros Bizjak To: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Uros Bizjak , Minchan Kim , Nitin Gupta , Andrew Morton Subject: [PATCH] zram: use try_cmpxchg in update_used_max Date: Tue, 18 Oct 2022 16:51:54 +0200 Message-Id: <20221018145154.3699-1-ubizjak@gmail.com> X-Mailer: git-send-email 2.37.3 MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Use try_cmpxchg instead of cmpxchg (*ptr, old, new) =3D=3D old in update_used_max. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). Also, reorder code a bit to remove additional compare and conditional jump from the assembly code. Together, hese two changes save 15 bytes from the function when compiled for x86_64. No functional change intended. Cc: Minchan Kim Cc: Nitin Gupta Cc: Andrew Morton Signed-off-by: Uros Bizjak --- drivers/block/zram/zram_drv.c | 13 +++++-------- 1 file changed, 5 insertions(+), 8 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 966aab902d19..87711ddf4b54 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -188,16 +188,13 @@ static void update_position(u32 *index, int *offset, = struct bio_vec *bvec) static inline void update_used_max(struct zram *zram, const unsigned long pages) { - unsigned long old_max, cur_max; - - old_max =3D atomic_long_read(&zram->stats.max_used_pages); + unsigned long cur_max =3D atomic_long_read(&zram->stats.max_used_pages); =20 do { - cur_max =3D old_max; - if (pages > cur_max) - old_max =3D atomic_long_cmpxchg( - &zram->stats.max_used_pages, cur_max, pages); - } while (old_max !=3D cur_max); + if (cur_max >=3D pages) + return; + } while (!atomic_long_try_cmpxchg(&zram->stats.max_used_pages, + &cur_max, pages)); } =20 static inline void zram_fill_page(void *ptr, unsigned long len, --=20 2.37.3