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=-0.8 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 1A43DC433E0 for ; Tue, 7 Jul 2020 18:01:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id D5674206E2 for ; Tue, 7 Jul 2020 18:01:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="K/h94cUG" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org D5674206E2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 886E76B00A9; Tue, 7 Jul 2020 14:01:13 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 836726B00AA; Tue, 7 Jul 2020 14:01:13 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 727126B00AB; Tue, 7 Jul 2020 14:01:13 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0215.hostedemail.com [216.40.44.215]) by kanga.kvack.org (Postfix) with ESMTP id 603B16B00A9 for ; Tue, 7 Jul 2020 14:01:13 -0400 (EDT) Received: from smtpin13.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id 239B02DFC for ; Tue, 7 Jul 2020 18:01:13 +0000 (UTC) X-FDA: 77012046426.13.brass94_32131a126eb6 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin13.hostedemail.com (Postfix) with ESMTP id 45DD31813F3E9 for ; Tue, 7 Jul 2020 18:00:58 +0000 (UTC) X-HE-Tag: brass94_32131a126eb6 X-Filterd-Recvd-Size: 4440 Received: from mail-ed1-f41.google.com (mail-ed1-f41.google.com [209.85.208.41]) by imf34.hostedemail.com (Postfix) with ESMTP for ; Tue, 7 Jul 2020 18:00:57 +0000 (UTC) Received: by mail-ed1-f41.google.com with SMTP id e22so39289530edq.8 for ; Tue, 07 Jul 2020 11:00:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=W8TPM5bdyg71dTiB8jNn7OZEEqQzG0GKM7OFFwfgiDw=; b=K/h94cUGQRAnMGuxd+caPCyuOVecpYq7lkiqe12dXivDNYSIS2W7nA/6d6xHUVwqHW L0PTHHjzgf/6x454ljLlcwPu0r2lI3MgpXuxkH6BNaHcONuq1rfWJwYKAQwYU8bpq7il WXS+iwx+ItTrJoS+D5ot8XXBigRVFMazQS/joqhV+4FbhyvFNBe2ix1LFu1+XP+hwIaU cw5Ma9+cM1/gO2BQrWp5LOrvxuphyExhv94teqkL2hjjdjDMwJxKVfwbsZQXhotZ8E3Y Grfny+Lv4W13MiVJBUEWg4sqUMPeHNyGCe/ZSjBCv9DHDPRxgiJWMr8Hl5V7WeQ4j5/r q+OQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to :content-transfer-encoding; bh=W8TPM5bdyg71dTiB8jNn7OZEEqQzG0GKM7OFFwfgiDw=; b=mjssBCC8qzY27QgVcQjYu2JS+JvDRWunb0eC1Vo7Zbmuen09x5cqLtfFeCZ22Ed1Cc xgM9vBwJ0nuf1TFt/mDys5cVTESVpCfb/bX9OhDocNmuYWwyhVyBJLGEc7cBmrN7C+Bt jlKmcBSNA6Tl4ZQc8D4W4eZD7Hkl8TzaSbMrpvtWxTXNzsxCzYX+DxDYobmXcKVitfSb 0eeWMfZOZ61qONOXbVsxwUyOcLwpNW3UDeyoCcH+KwMVz1hsugQaaKVtyu5LgRVprd9A njX8cbnxUR55OZ2O4II9rHmkmDPPtmk/yirDqPn06PyOHDZCaK+1ax5yFDcEnhZ1iKmt bHgA== X-Gm-Message-State: AOAM530RBd9b1vjH3xeCV7TYH5/hjPPorbdNqf+pHcLaNZFY3gzy7LEM Uvl5T+Hn5XQnWlQ59oZSLpbl/5SXDP5hUl87KL0= X-Google-Smtp-Source: ABdhPJykMRStnd4trilBtj5i4D4gaKZ5GcjXdYTfXEawrY7dsNiAXwuo1XMh/Xr0OoySQVDWaF1ZZzJ+glTAoiYu2/4= X-Received: by 2002:a05:6402:377:: with SMTP id s23mr63936839edw.200.1594144856588; Tue, 07 Jul 2020 11:00:56 -0700 (PDT) MIME-Version: 1.0 From: Yang Shi Date: Tue, 7 Jul 2020 11:00:16 -0700 Message-ID: Subject: [RFC] Kill THP deferred split queue? To: "Kirill A. Shutemov" , Linux MM , Linux Kernel Mailing List Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 45DD31813F3E9 X-Spamd-Result: default: False [0.00 / 100.00] X-Rspamd-Server: rspam05 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: Hi folks, The THP deferred split queue is used to store PTE mapped THP (i.e. partial unmapped THP) then they will get split by deferred split shrinker when memory pressure kicks in. Now the page reclaim could handle such cases nicely without calling the shrinker. Since the THPs on deferred split queue is not PMD mapped so they will be split unconditionally, then the unmapped sub pages would get freed. Please see the below code snippet: if (PageTransHuge(page)) { /* cannot split THP, skip it */ if (!can_split_huge_page(page, NULL= )) goto activate_locked; /* * Split pages without a PMD map ri= ght * away. Chances are some or all of= the * tail pages can be freed without = IO. */ if (!compound_mapcount(page) && split_huge_page_to_list(page, page_li= st)) goto activate_locked; } Then the unmapped pages will be moved to free_list by move_pages_to_lru() called by shrink_inactive_list(). The mapped sub pages will be kept on LRU. So, it does exactly the same thing as deferred split shrinker and at the exact same timing. The only benefit of shrinker is they can be split and freed via "echo 2 > /proc/sys/vm/drop_caches=E2=80=9D, but I'm not sure how many people rel= y on this? The benefit of killing deferred split queue is code simplification. Any comment is welcome. Thanks, Yang