From nobody Fri Jun 19 18:04:21 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 E34DAC433FE for ; Thu, 31 Mar 2022 04:08:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229692AbiCaEKE (ORCPT ); Thu, 31 Mar 2022 00:10:04 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51066 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229610AbiCaEJU (ORCPT ); Thu, 31 Mar 2022 00:09:20 -0400 Received: from mail-qk1-x731.google.com (mail-qk1-x731.google.com [IPv6:2607:f8b0:4864:20::731]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9C53C170084; Wed, 30 Mar 2022 20:56:59 -0700 (PDT) Received: by mail-qk1-x731.google.com with SMTP id g8so18827481qke.2; Wed, 30 Mar 2022 20:56:59 -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=tYlHPxM0iDi5VXE98hgeozahqYJk78JaFFeV+qzNw5U=; b=mTmT7+N63PXuIwB75+CKvFI6cw/jzFICsKFlmrX98DCY4KgVobDxkUkLrPbILjWEVd zOpsJzohasYTU2cri3mhczLOHO+85IFJWAcIzlnZ8sYbVwKoGAyN3ZrI0vtWoa7Qu3eu CsqMCtZFWjlutPRNC7lKg6mZUe8Sh5MDsmm5GAacxLBCKifK/EA4n2cFQBko12jzZ9sS WKQUNIcMTTE9y9FtrLpqhMIlKbYvWdq1U+ww/1au0hwzkHBamg7+Phf1Jd5WuYcisENx lCO2kL34hCyKaR+8Rf8wpTYtiFvSRdvzMZ6EfRXAZk+xbijJO3mI2cpMPxQ0aZw2TTYf kybg== 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=tYlHPxM0iDi5VXE98hgeozahqYJk78JaFFeV+qzNw5U=; b=STUmnVhXh3Sl9XglOkQc0q42kfRim7WNYEzUWi3rEpWsak8Bo6/GdGb0uFif48+39l MDu5uiw2YHoHws3uWmyTOkkceq6y3WAr8IPjocqb1k/rJXFV9Z7RH3T4eylr/ke3QcjJ XK4AmlGHGuqjb/+YfFGBCVh5z9MjAdpe5+SE17gIZyiZEnfqxJ35AYpVBnacvZPzq1Om IY8P6NLbrP/GEH/X/6fh1xel6nG34idP+lZDZBQrAmfPZ/OG/YzwO6lG3mxybkTgXqGk AfhCaNbvBUJvVi8UqZPPH/yVDw1kXCkGnxNN8f2quvDKfJ+F5A+BMkkittxpkhMtKVIB B1xQ== X-Gm-Message-State: AOAM5317i4sAHqNIthshm6txwNYl0SRLQpYDUY9za6OmGu3zO+ivoggd bUXnHg0JH+c2n+y8Qwb3nQGP/gc3O/o= X-Google-Smtp-Source: ABdhPJzyPrz0p+L/ALJneQJkAZo6ZUHwvs4kf6iDO0DACiqXPcs8bbEYZ5Igo5IyJWR4z4os6/CMDA== X-Received: by 2002:a37:9503:0:b0:67e:977:9ff6 with SMTP id x3-20020a379503000000b0067e09779ff6mr2101575qkd.10.1648699018774; Wed, 30 Mar 2022 20:56:58 -0700 (PDT) Received: from localhost.localdomain ([193.203.214.57]) by smtp.gmail.com with ESMTPSA id f17-20020ac87f11000000b002e1e831366asm18698404qtk.77.2022.03.30.20.56.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Mar 2022 20:56:57 -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, saravanand@fb.com, minchan@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, jhubbard@nvidia.com, xu xin , Ran Xiaokai Subject: [PATCH v5] mm/vmstat: add events for ksm cow Date: Thu, 31 Mar 2022 03:56:17 +0000 Message-Id: <20220331035616.2390805-1-yang.yang29@zte.com.cn> X-Mailer: git-send-email 2.25.1 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" 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 --- 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. v5: - fix compile error when CONFIG_SWAP is not set --- Documentation/admin-guide/mm/ksm.rst | 18 ++++++++++++++++++ include/linux/vm_event_item.h | 3 +++ mm/memory.c | 4 ++++ mm/vmstat.c | 3 +++ 4 files changed, 28 insertions(+) diff --git a/Documentation/admin-guide/mm/ksm.rst b/Documentation/admin-gui= de/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`` ra= tio is limited by the ``max_page_sharing`` tunable. To increase the ratio ``max_page_sharing`` m= ust be increased accordingly. =20 +Monitoring KSM events +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D + +There are some counters in /proc/vmstat that may be used to monitor KSM ev= ents. +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 pag= e. + -- 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..e83967e4c20e 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -133,6 +133,9 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, KSM_SWPIN_COPY, #endif #endif +#ifdef CONFIG_KSM + COW_KSM, +#endif #ifdef CONFIG_X86 DIRECT_MAP_LEVEL2_SPLIT, DIRECT_MAP_LEVEL3_SPLIT, 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); =20 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); } =20 diff --git a/mm/vmstat.c b/mm/vmstat.c index d5cc8d739fac..79015f144b15 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1392,6 +1392,9 @@ const char * const vmstat_text[] =3D { "ksm_swpin_copy", #endif #endif +#ifdef CONFIG_KSM + "cow_ksm", +#endif #ifdef CONFIG_X86 "direct_map_level2_splits", "direct_map_level3_splits", --=20 2.25.1