From patchwork Wed Mar 30 08:26:41 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: CGEL X-Patchwork-Id: 12795582 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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id CFF52C433F5 for ; Wed, 30 Mar 2022 08:28:16 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 47CC08D0003; Wed, 30 Mar 2022 04:28:16 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 42C8A8D0001; Wed, 30 Mar 2022 04:28:16 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 2CD868D0003; Wed, 30 Mar 2022 04:28:16 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0056.hostedemail.com [216.40.44.56]) by kanga.kvack.org (Postfix) with ESMTP id 1B1D78D0001 for ; Wed, 30 Mar 2022 04:28:16 -0400 (EDT) Received: from smtpin21.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id BB973A5BC6 for ; Wed, 30 Mar 2022 08:28:15 +0000 (UTC) X-FDA: 79300375350.21.E5B7B3B Received: from mail-qt1-f172.google.com (mail-qt1-f172.google.com [209.85.160.172]) by imf23.hostedemail.com (Postfix) with ESMTP id 64903140005 for ; Wed, 30 Mar 2022 08:28:15 +0000 (UTC) Received: by mail-qt1-f172.google.com with SMTP id s11so17462476qtc.3 for ; Wed, 30 Mar 2022 01:28:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1H14edHrexPdZSsbFfB5+DKs6PQ4z+rHst+0leIL3Cw=; b=i7x2SIOEfBJv2Erzs9AxsTqiUf701YydhIxCj1fTKKaFN0qYV0gp/MQNT9h3UwXKRC xV3XDXqW2EXCiJT9G9Rx5Cfobn95y2WQGBxAbcWtdnQNRSrzwrgG8ehwxdMpmYdX6okR wGGjBO3V/Mjme2aJdXwoU4Yx/vJOx6NU6lYb44qpk9ECHH1Dd9Gg4GcoLI1B8DCz7/ed 3yqMS0E+FdhP96QjyLPbuPbBHg5aAZnYXOwEShyTBpLqLf+hyOxLxTWPexM+xgI5hyk6 kNGAhLDIDcfC1zu7pt05sUI+npHrSPPemlweu5duUlRSmEb0ZCjHtCGekZ+SiH6GbPfX YvMA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:mime-version :content-transfer-encoding; bh=1H14edHrexPdZSsbFfB5+DKs6PQ4z+rHst+0leIL3Cw=; b=RaFnQvIiurTf2trTP4h/plGE+X8syK0TvV5ywncfFLNiXbHGpeQwxs56cEomDvJh7X h+CZBDjcJR5HiLnKAhXsBTOIb8atQ0ejNqxLsKsXNc7uaD3DHjki3xugBrg8hBvRQzgS Ki3fWjZJvxwOMLmAGgwGdIAXuOvVOEoNV8NSHDVXAeV8l+IkukI0KPYY3ZnsmD+Ixpnv Y1nGkkH4LRTUWgreumJYoUKBB5XqKJhDLwJ8XbEZJJLhMXlGs/8piHPPztRgEz79k6Ho QD9R+qqb8zrEOt5gMoKMlYSO0sFmEr6NNhZoJxFt38GIpnctDq6uO7FJGiyAL2f3JDAa qV8w== X-Gm-Message-State: AOAM532wR3mtnQGsixPFA3KLSlsdL/ymv2PianvNAHp6bXlSJtaOgdVN 7s0FWwPKH67t5geZc52exrw= X-Google-Smtp-Source: ABdhPJwRlfo0Y8TA4yle0PUfqmJwdRVeb7L11mlOl/AfeZ/BE1DHPAj/1gDlLvVv3D8gTQB9emF2UQ== X-Received: by 2002:ac8:5787:0:b0:2e1:c837:64ed with SMTP id v7-20020ac85787000000b002e1c83764edmr31903754qta.98.1648628894609; Wed, 30 Mar 2022 01:28:14 -0700 (PDT) Received: from localhost.localdomain ([193.203.214.57]) by smtp.gmail.com with ESMTPSA id d11-20020a05620a166b00b0067e380258e7sm10403966qko.73.2022.03.30.01.28.09 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Mar 2022 01:28:13 -0700 (PDT) From: cgel.zte@gmail.com X-Google-Original-From: yang.yang29@zte.com.cn To: akpm@linux-foundation.org, david@redhat.com, willy@infradead.org Cc: corbet@lwn.net, yang.yang29@zte.com.cn, yang.shi@linux.alibaba.com, dave.hansen@linux.intel.com, jhubbard@nvidia.com, saravanand@fb.com, minchan@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, xu xin , Ran Xiaokai Subject: [PATCH v4] mm/vmstat: add events for ksm cow Date: Wed, 30 Mar 2022 08:26:41 +0000 Message-Id: <20220330082640.2381401-1-yang.yang29@zte.com.cn> X-Mailer: git-send-email 2.25.1 MIME-Version: 1.0 X-Stat-Signature: nhh6cos1ky4qdd9rytmynjh69gt58kac X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 64903140005 Authentication-Results: imf23.hostedemail.com; dkim=pass header.d=gmail.com header.s=20210112 header.b=i7x2SIOE; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (imf23.hostedemail.com: domain of cgel.zte@gmail.com designates 209.85.160.172 as permitted sender) smtp.mailfrom=cgel.zte@gmail.com X-Rspam-User: X-HE-Tag: 1648628895-210281 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: From: Yang Yang Users may use ksm by calling madvise(, , MADV_MERGEABLE) when they want to save memory, it's a tradeoff by suffering delay on ksm cow. Users can get to know how much memory ksm saved by reading /sys/kernel/mm/ksm/pages_sharing, but they don't know what's the costs of ksm cow, and this is important of some delay sensitive tasks. So add ksm cow events to help users evaluate whether or how to use ksm. Also update /Documentation/admin-guide/mm/ksm.rst with new added events. Signed-off-by: Yang Yang Reviewed-by: David Hildenbrand Reviewed-by: xu xin Reviewed-by: Ran Xiaokai Reported-by: kernel test robot Reported-by: kernel test robot --- v2: - fix compile error when CONFIG_KSM is not set v3: - delete KSM_COW_FAIL event v4: - modify /Documentation/admin-guide/mm/ksm.rst. And let cow_ksm before - ksm_swpin_copy, so if new cow_* event could add before cow_ksm. --- Documentation/admin-guide/mm/ksm.rst | 18 ++++++++++++++++++ include/linux/vm_event_item.h | 1 + mm/memory.c | 4 ++++ mm/vmstat.c | 1 + 4 files changed, 24 insertions(+) diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-guide/mm/ksm.rst index 97d816791aca..b244f0202a03 100644 --- a/Documentation/admin-guide/mm/ksm.rst +++ b/Documentation/admin-guide/mm/ksm.rst @@ -184,6 +184,24 @@ The maximum possible ``pages_sharing/pages_shared`` ratio is limited by the ``max_page_sharing`` tunable. To increase the ratio ``max_page_sharing`` must be increased accordingly. +Monitoring KSM events +===================== + +There are some counters in /proc/vmstat that may be used to monitor KSM events. +KSM might help save memory, it's a tradeoff by may suffering delay on KSM COW +or on swapping in copy. Those events could help users evaluate whether or how +to use KSM. For example, if cow_ksm increases too fast, user may decrease the +range of madvise(, , MADV_MERGEABLE). + +cow_ksm + is incremented every time a KSM page triggers copy on write (COW) + when users try to write to a KSM page, we have to make a copy. + +ksm_swpin_copy + is incremented every time a KSM page is copied when swapping in + note that KSM page might be copied when swapping in because do_swap_page() + cannot do all the locking needed to reconstitute a cross-anon_vma KSM page. + -- Izik Eidus, Hugh Dickins, 17 Nov 2009 diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index 16a0a4fd000b..74ec4b6a9ed0 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -130,6 +130,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, SWAP_RA, SWAP_RA_HIT, #ifdef CONFIG_KSM + COW_KSM, KSM_SWPIN_COPY, #endif #endif diff --git a/mm/memory.c b/mm/memory.c index 4111f97c91a0..12925ceaf745 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3339,6 +3339,10 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) get_page(vmf->page); pte_unmap_unlock(vmf->pte, vmf->ptl); +#ifdef CONFIG_KSM + if (PageKsm(vmf->page)) + count_vm_event(COW_KSM); +#endif return wp_page_copy(vmf); } diff --git a/mm/vmstat.c b/mm/vmstat.c index d5cc8d739fac..250ae0652740 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1389,6 +1389,7 @@ const char * const vmstat_text[] = { "swap_ra", "swap_ra_hit", #ifdef CONFIG_KSM + "cow_ksm", "ksm_swpin_copy", #endif #endif