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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 91500C433EF for ; Thu, 20 Jan 2022 01:12:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237545AbiATBMK (ORCPT ); Wed, 19 Jan 2022 20:12:10 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50270 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233976AbiATBMJ (ORCPT ); Wed, 19 Jan 2022 20:12:09 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A957DC061574 for ; Wed, 19 Jan 2022 17:12:09 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id z15-20020a25bb0f000000b00613388c7d99so8525086ybg.8 for ; Wed, 19 Jan 2022 17:12:09 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=date:message-id:mime-version:subject:from:to:cc; bh=tA2eESNey0k0XP9lk3g/bAUxhAQW5/EDDgeejjFfXNg=; b=J3HQT9krlZpsQHQTFN3l8Z8u2Xf/3ewg0BZLCCsSyi7tFH4eLStKDf57djLK731CyH 2r766eOGcq9rdqLNOJrGcFlsrzoPV46P5LdGiKJmson3U5GH8I/is7v0u5OMLh/I51pU n4ocALKdQwW+oeKJENm84eCGpAsDqPaYUxQmMIBz3zGWoVWohLW3g3a+rJsXUAVzrSIl Ecl1bJw/BpuRnv1x/vgqFs/zDoTBSHDe1YyhkOThvZc1vjQnStHhiSL9t0CynG+n5mse Jw2Jhj1G8Ay/lodL/w4dwWnjl3tqe1F/qt6981+t+OpYfhWHQD9DeFMbbgOpYrTHQbuY cfbQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:message-id:mime-version:subject:from:to:cc; bh=tA2eESNey0k0XP9lk3g/bAUxhAQW5/EDDgeejjFfXNg=; b=n5Jumd7szEjvzOt5XI9exnwvXCWs5PmcK4AWyN4JnPWiaFwIOyMn5bzxKutmZDNlDD Pe8d04aZ8f8e8pNkVK4jbIkLT2yI4On/G2TVpUAKUd/qeljZ3fiG1l0rR4iPqMmuMbUg bx4J0SW3OUjXCswDwDSrsdsH+VVCkmTT2SSBu8WtjU98cUUnJKzkahYVU9a6KOv7qT1s Ca/rG5sCg2oJLTvKM7vCU8lrndTTHFQiXQeOGx3F4QgAq4EKco+83spmsTLoGr6uMfi2 plC7Uia8vLPYdjEM7Uknf4XHft8aPpyE8s+ae+Mstk0v6zRkb2pYGC6bHm7hkHZhKaq0 9Weg== X-Gm-Message-State: AOAM5332jH97qLWs3ogEZiSb5QUrTftCYTK7HrubKun3djwzmGPgcLzu yEN7bg63zHUB58/5gcfyntrPSjc= X-Google-Smtp-Source: ABdhPJz3mwdM+0As6FN3WKubqoUI/B4hcSVbjvP6uZO/jii6WDL2eFvY2vyHyvkgUT+SrC7/zokdGqk= X-Received: from pcc-desktop.svl.corp.google.com ([2620:15c:2ce:200:7641:d112:dd90:7ea1]) (user=pcc job=sendgmr) by 2002:a25:bb45:: with SMTP id b5mr27616743ybk.174.1642641128808; Wed, 19 Jan 2022 17:12:08 -0800 (PST) Date: Wed, 19 Jan 2022 17:11:59 -0800 Message-Id: <20220120011200.1322836-1-pcc@google.com> Mime-Version: 1.0 X-Mailer: git-send-email 2.34.1.703.g22d0c6ccf7-goog Subject: [PATCH v2] mm/mmzone.c: use try_cmpxchg() in page_cpupid_xchg_last() From: Peter Collingbourne To: Andrey Konovalov , Andrew Morton Cc: Peter Collingbourne , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Peter Zijlstra , Mel Gorman Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This will let us avoid an additional read from page->flags when retrying the compare-exchange on some architectures. Suggested-by: Peter Zijlstra Signed-off-by: Peter Collingbourne Link: https://linux-review.googlesource.com/id/I2e1f5b5b080ac9c4e0eb7f98768dba6fd7821693 --- mm/mmzone.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/mm/mmzone.c b/mm/mmzone.c index eb89d6e018e2..d8a9b0e1b526 100644 --- a/mm/mmzone.c +++ b/mm/mmzone.c @@ -89,13 +89,14 @@ int page_cpupid_xchg_last(struct page *page, int cpupid) unsigned long old_flags, flags; int last_cpupid; + old_flags = READ_ONCE(page->flags); do { - old_flags = flags = page->flags; - last_cpupid = page_cpupid_last(page); + flags = old_flags; + last_cpupid = (flags >> LAST_CPUPID_PGSHIFT) & LAST_CPUPID_MASK; flags &= ~(LAST_CPUPID_MASK << LAST_CPUPID_PGSHIFT); flags |= (cpupid & LAST_CPUPID_MASK) << LAST_CPUPID_PGSHIFT; - } while (unlikely(cmpxchg(&page->flags, old_flags, flags) != old_flags)); + } while (unlikely(!try_cmpxchg(&page->flags, &old_flags, flags))); return last_cpupid; } -- 2.34.1.703.g22d0c6ccf7-goog