From nobody Mon Jun 22 13:25:10 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 12D1FC433EF for ; Wed, 23 Mar 2022 07:57:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S242356AbiCWH7M (ORCPT ); Wed, 23 Mar 2022 03:59:12 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42068 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232884AbiCWH7K (ORCPT ); Wed, 23 Mar 2022 03:59:10 -0400 Received: from mail-qt1-x830.google.com (mail-qt1-x830.google.com [IPv6:2607:f8b0:4864:20::830]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D17144B873 for ; Wed, 23 Mar 2022 00:57:40 -0700 (PDT) Received: by mail-qt1-x830.google.com with SMTP id bp39so525994qtb.6 for ; Wed, 23 Mar 2022 00:57:40 -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=r41iKAI43c+0K6+pKFWIsdBKfHtyHD+d9VR6NqUvZmg=; b=m3gv09RuBTI4VChKq3U2t+BbGYngVCzLIJfBaobFg4LwwJM0aDdU/QoOD98YFedd95 aJ1t6X9R0wUbOrVp9vDmWPA33pJ0MQiHq9gDnqAaLzHoLDDjmQWx1H94aY93EgJK6CX+ EbdEYBArwVIka0fvMsLR5nQ8TLyHlG7zeTH+1vqIrE7vSNAYGkENxPJHUC585mBJE1FN EWeNX5XPWaxojKBAZE9UAdT3+MZAsE//sNTU9ZqlO8+TmNNDOSnv4LNQIfMIwSA2paS3 d45ThDhNpesSVsOX1V9gIDpBwccRU7Ikuanp3jaIE1uPFRhy85oqCgDfL4nfpUZjX53u Wudw== 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=r41iKAI43c+0K6+pKFWIsdBKfHtyHD+d9VR6NqUvZmg=; b=oEYGuTDDAs4MqKADfuz0tazvqjvCueSI9ivXra3NGb8tjmLpcIYQKpIQdB7MBSk//2 OBCke7x2dBUrVfZ/BdJmgOih6DAatF9gkRTFVi/yMUHdAjjjH6illWhfqlvZr2df073C VFr6sVTU9o2vCHK2NIaBOM0gygw4IpjzqI394lY8LJgMlL4tjYOJs/dwmiWtyJknXnw6 0HdvE7jaSXDnotyn1ULLAxoDWx2rVmIOeR47pFJlzUA2/+AnPo+lNFiLCjTY8M2plB2+ KNPveWw4KIrkgTXBY5D8JyjXZ4I+H31DxkBE+lg9JT+hUrxOPzxY0x8sWHC3/HmVQien mqKg== X-Gm-Message-State: AOAM533aUVewKKN9ofNkFgq30OJt5wq9RdsMya/I3a3W3eiCbu3riC7y 3LCqAoNmsdFc7YNNsSYGkR4= X-Google-Smtp-Source: ABdhPJxwFkDY9Hb9zPqDADDHQyZysCI6txqKo+3o0s3vLkqC5uOLFGlD56M4b7QZMWRvO+CSQukraQ== X-Received: by 2002:ac8:5e0e:0:b0:2e1:b6b7:10e8 with SMTP id h14-20020ac85e0e000000b002e1b6b710e8mr23229981qtx.172.1648022259497; Wed, 23 Mar 2022 00:57:39 -0700 (PDT) Received: from localhost.localdomain ([193.203.214.57]) by smtp.gmail.com with ESMTPSA id q8-20020a05622a030800b002e1c9304db8sm15641608qtw.38.2022.03.23.00.57.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 23 Mar 2022 00:57:38 -0700 (PDT) From: cgel.zte@gmail.com X-Google-Original-From: yang.yang29@zte.com.cn To: akpm@linux-foundation.org, david@redhat.com Cc: yang.yang29@zte.com.cn, dave.hansen@linux.intel.com, ran.xiaokai@zte.com.cn, yang.shi@linux.alibaba.com, saravanand@fb.com, minchan@kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, xu xin Subject: [PATCH v2] mm/vmstat: add events for ksm cow Date: Wed, 23 Mar 2022 07:57:15 +0000 Message-Id: <20220323075714.2345743-1-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. Signed-off-by: Yang Yang Reviewed-by: xu xin Reviewed-by: Ran Xiaokai --- v2: - fix compile error when CONFIG_KSM is not set --- include/linux/vm_event_item.h | 2 ++ mm/memory.c | 20 +++++++++++++++++--- mm/vmstat.c | 2 ++ 3 files changed, 21 insertions(+), 3 deletions(-) diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h index 16a0a4fd000b..6f32be04212f 100644 --- a/include/linux/vm_event_item.h +++ b/include/linux/vm_event_item.h @@ -131,6 +131,8 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT, SWAP_RA_HIT, #ifdef CONFIG_KSM KSM_SWPIN_COPY, + KSM_COW_SUCCESS, + KSM_COW_FAIL, #endif #endif #ifdef CONFIG_X86 diff --git a/mm/memory.c b/mm/memory.c index 4111f97c91a0..c24d5f04fab5 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3257,6 +3257,8 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) __releases(vmf->ptl) { struct vm_area_struct *vma =3D vmf->vma; + vm_fault_t ret =3D 0; + bool ksm =3D 0; =20 if (userfaultfd_pte_wp(vma, *vmf->pte)) { pte_unmap_unlock(vmf->pte, vmf->ptl); @@ -3294,6 +3296,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) */ if (PageAnon(vmf->page)) { struct page *page =3D vmf->page; + ksm =3D PageKsm(page); =20 /* * We have to verify under page lock: these early checks are @@ -3302,7 +3305,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) * * PageKsm() doesn't necessarily raise the page refcount. */ - if (PageKsm(page) || page_count(page) > 3) + if (ksm || page_count(page) > 3) goto copy; if (!PageLRU(page)) /* @@ -3316,7 +3319,7 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) goto copy; if (PageSwapCache(page)) try_to_free_swap(page); - if (PageKsm(page) || page_count(page) !=3D 1) { + if (ksm || page_count(page) !=3D 1) { unlock_page(page); goto copy; } @@ -3339,7 +3342,18 @@ static vm_fault_t do_wp_page(struct vm_fault *vmf) get_page(vmf->page); =20 pte_unmap_unlock(vmf->pte, vmf->ptl); - return wp_page_copy(vmf); + ret =3D wp_page_copy(vmf); + +#ifdef CONFIG_KSM + if (ksm) { + if (unlikely(ret & VM_FAULT_ERROR)) + count_vm_event(KSM_COW_FAIL); + else + count_vm_event(KSM_COW_SUCCESS); + } +#endif + + return ret; } =20 static void unmap_mapping_range_vma(struct vm_area_struct *vma, diff --git a/mm/vmstat.c b/mm/vmstat.c index d5cc8d739fac..a2c29a5206ec 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1390,6 +1390,8 @@ const char * const vmstat_text[] =3D { "swap_ra_hit", #ifdef CONFIG_KSM "ksm_swpin_copy", + "ksm_cow_success", + "ksm_cow_fail", #endif #endif #ifdef CONFIG_X86 --=20 2.25.1