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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id 97463D36113 for ; Tue, 5 Nov 2024 19:35:46 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id D80A66B0085; Tue, 5 Nov 2024 14:35:45 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id D30D16B0089; Tue, 5 Nov 2024 14:35:45 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id C1F956B008A; Tue, 5 Nov 2024 14:35:45 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id A5BC96B0085 for ; Tue, 5 Nov 2024 14:35:45 -0500 (EST) Received: from smtpin17.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay08.hostedemail.com (Postfix) with ESMTP id 1A0B01416F4 for ; Tue, 5 Nov 2024 19:35:45 +0000 (UTC) X-FDA: 82753043940.17.A7B1FD6 Received: from mail-qv1-f44.google.com (mail-qv1-f44.google.com [209.85.219.44]) by imf12.hostedemail.com (Postfix) with ESMTP id 1541B4001B for ; Tue, 5 Nov 2024 19:35:27 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=gIJjP4SC; spf=pass (imf12.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.219.44 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1730835159; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=34EBB02qLglczeLB5qc7NWhxtQbeKZXTV9/H28It/fc=; b=tI6diPg3XtHLG43tMrk+j5bFCOPaI3h2o4unw0kE+dPHvEs2XhwTUPTxzyDQG/h0L8C0JO p2qapdVvIb1xN5KTD2JzBOcOmTG0p0DQh0OUHWRGBWbYdK4irD2zgSEhp0QuaOfywj3wpv B7gb9HGbO//5SeFa7XjXSeGpX6JpLTQ= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20230601 header.b=gIJjP4SC; spf=pass (imf12.hostedemail.com: domain of nphamcs@gmail.com designates 209.85.219.44 as permitted sender) smtp.mailfrom=nphamcs@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1730835159; a=rsa-sha256; cv=none; b=eYjgPZNCe1ds0rvoDyjGFtz4C3wq90Dmf87YrSBA4qMNO7uAn/RJhzI8RMrCvxRST6t1fx P2ots4E+ydSr5LWlqQ543vszW8nrgdIto6Yjvq5uH6+3L5EmDCWwPOVc5aorTNc22bJDtU mdDLaDWZ3W+ToXuB4iG7SEosAhBfmic= Received: by mail-qv1-f44.google.com with SMTP id 6a1803df08f44-6cbce16d151so37894716d6.2 for ; Tue, 05 Nov 2024 11:35:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1730835342; x=1731440142; darn=kvack.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=34EBB02qLglczeLB5qc7NWhxtQbeKZXTV9/H28It/fc=; b=gIJjP4SCEKBV0xwlGT9j0zo8aVKOlxkLGJ7c1biT3Oh0R61vSKzNvDTXgrmwYnsk5Z +6B6FdRSOmP0VuBG5viFPTML4z2QA44KJ5sR+m4dmP3PPoRzzbbsqhCHhVu/FWEFUCKu +BHAxA6RbGkJwzHm1gUZjT4DGgq6iEbp4bSDVY2OAorulN1/qTKPi/HyVmRBTyWfRWja mVMrYX3zTNim+2zS0SA72VP6G4rateHsWorSFOp3iew8X9hBZ4ss+KNCcEAO45R0E+IF CsjINP7Qi9MnAV1/UHYgHd8y0TI9HQBAzjZu3XPTjHJFKr43Ee9eFVQ7k7DToqtDIW+s hxEA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1730835342; x=1731440142; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=34EBB02qLglczeLB5qc7NWhxtQbeKZXTV9/H28It/fc=; b=A9FLA5WPoymH53a1mfajX4vgYvwoWGasC5UrrJAnuWKtFILOvdAuEbUttfBIYgpTEd AZxEWlx4wr27hgDlkrDL2eOtBrb6elCcnYlR+Y+zSuvOZIStyMVtgt2r+sOa40EyX1qh HdmlJLxi0jOtbS/XgR7k8A6+8yAmAv5n4ivt/TLwSGIiEXjeZi5XaAy5Jlq79yBCUzYn MRqHcdwHiuH9W9BZRuJQujEb5D7yrIvmPkMDR2ARNCt1GabsYkkY7OZOUqEtoZ5wvohd ZmGgwTnnSPpdRCFgDpgH8A0ZhAsQceOvUHkuwBinmdW0PxQX50U+6s9hLYpU1XiAk5eC RGMg== X-Forwarded-Encrypted: i=1; AJvYcCUaOtoo5657BQXzOHCgqI8lB+XNcjyFlLXJQp24HkZ4WvLDiEZ9oWPt5vhAiYKkzyvRXFaszZNhkA==@kvack.org X-Gm-Message-State: AOJu0Yw8WNLNUU5YK/kWYphuDFhz2EyIuO5FkkIwmT0izOOhutYDkcQi pq58be9rvNuLMQoLRR967dgv0FaPBiOKOT1o1r3aRIxE04uSPi2RW4FD3j1I+6qxK+4qmrta5AZ MP0ayhovxtQdrfQINErgk3SPYmZs= X-Google-Smtp-Source: AGHT+IHUiYLp/JoQQjAX5DzYlllLrbDkaCy2q+uKnPJMvfHv4JT7Du9uZLkU/K7awIA3IagbTglqj9Izb1fwu4yRa/Q= X-Received: by 2002:a05:6214:5d93:b0:6c1:6e3a:6d17 with SMTP id 6a1803df08f44-6d185674992mr551096586d6.6.1730835342334; Tue, 05 Nov 2024 11:35:42 -0800 (PST) MIME-Version: 1.0 References: <20241102101240.35072-1-21cnbao@gmail.com> In-Reply-To: <20241102101240.35072-1-21cnbao@gmail.com> From: Nhat Pham Date: Tue, 5 Nov 2024 11:35:31 -0800 Message-ID: Subject: Re: [PATCH v2] mm: count zeromap read and set for swapout and swapin To: Barry Song <21cnbao@gmail.com> Cc: akpm@linux-foundation.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Barry Song , Usama Arif , Chengming Zhou , Yosry Ahmed , Johannes Weiner , David Hildenbrand , Hugh Dickins , Matthew Wilcox , Shakeel Butt , Andi Kleen , Baolin Wang , Chris Li , "Huang, Ying" , Kairui Song , Ryan Roberts Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 1541B4001B X-Stat-Signature: xke943146qgy6sqtpz85t74cgjfyjpt3 X-Rspam-User: X-HE-Tag: 1730835327-594773 X-HE-Meta: U2FsdGVkX191noNAPQgbqCNdsfyqLBF4EFMSHLQJ0+BjNT+/nmAPn2JwiQOp4DmRtLjn2nHBXGVQRB7R7KeFJVVMFyqk35O+9rfVlibx+B6JjKUFPi+lRQiBw/avrNnSXQV5ievt5PCXiFtxAvuJeKgRdsklSsaN0e8yiU2WyivBXjBWZwls1GGXwM9pHMAhqc2lsjE7qpjOGKWd4TsR4GN5mETuew6iNSkwKzhR9P7eB9VBFRXGvJ48Fz3xcfDsfj2nmKZdqpGuv1BP0se6ZrbSdZanoPwwtkK3Z48uXQRI2WGZULJpSMWN8HRBeTAq7xGDozFLOikpedyJBeqBj6SrZ6JV4NS3AW9d4ACpEzkI3cOsdVmim/x8IakMknUhtNzX7Yao5+DgItWZK4Hzvoa+ySENH6VKa4+jDTy+LDO2hYmvrdYA/u5CbZVUAZOwGHUiTJZWKzyS5JvtdWbsR5Vs1cLPB1yjhPgrva37++k21ftedFT3Z8ZK3QVCAtmDhWj60lj/vBu7AZJvkpztp4SSxwZyErMtd0YSKXcx2UVYcsABpEdKTAxR8dMc2I4e5MI2wAaoihM7OchJvoVB01jBZIxqmYUHn1acl624Km4AInh3vv1m3TIDijtflDSPNp+lo2NsO+wcm1o8KbDdMogp9CGa1c7H8VZz1ec4lUgCUT5GafnRnWG7j7kA0/Tj6Ms+9LImxsm+qoFmhOuo44KkqHSiowEwn0E9yf6BwWl/2osh+9+uBgaZK6ncZd6f8b5+EehTD7KebvwI1rva6byoeJBcmu9EJohtrTqqSC55RrhTzj9gYZFvA90ksU2KjHYHp3+y9xyc20WOL7BSz7qGsVxx1av3y3Xd6TOZgXkRUvcQz2J9xinEH6TN+uheNvttsrI2OcHPM3TmCpslmDikSqBFt7hdTifb9/29vSQuHthS1KDbd2l3hsy5hfHs/t46OxtoRP0rlmjIYPo 4k9YXFQf 6qvdzItQoNKEqHY4uaKtXXUZ9FirmzEVhNvGrwlXJH24gnoPSbLeeR+BYKjy8SHqpZUwmFqO8glfnUPjJHai3mx3vhaQasNKB/Nm+fP1Bk4rQyU3CSZzyognfMSyZcuy+hMrMLZR9jmPiV17ZOZxD7cQsxvHr8IWBtFiBKfQ3y4SP2i14U9MqfomOdt5clTskbZkDZVhMtSznKG6jvBA6He/PwJo/7VyNy6oKePNThoDBkOfQhI7SWtnmmSCAbItis/NvpClIzp3RZEhs56knXkIFrL2q93SqdclHrAl+kxeT7Wc/vKlSZ/AoVRZQVZ7E3RXzKpyEmyat2ucJZFS3cT9ufeYVgK9Dby/9qaipfIU67bSN+v7ufncRXg== 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: List-Subscribe: List-Unsubscribe: On Sat, Nov 2, 2024 at 3:12=E2=80=AFAM Barry Song <21cnbao@gmail.com> wrote= : > > From: Barry Song > > When the proportion of folios from the zero map is small, missing their > accounting may not significantly impact profiling. However, it=E2=80=99s = easy > to construct a scenario where this becomes an issue=E2=80=94for example, > allocating 1 GB of memory, writing zeros from userspace, followed by > MADV_PAGEOUT, and then swapping it back in. In this case, the swap-out > and swap-in counts seem to vanish into a black hole, potentially > causing semantic ambiguity. > > We have two ways to address this: > > 1. Add a separate counter specifically for the zero map. > 2. Continue using the current accounting, treating the zero map like > a normal backend. (This aligns with the current behavior of zRAM > when supporting same-page fills at the device level.) > > This patch adopts option 1 as pswpin/pswpout counters are that they > only apply to IO done directly to the backend device (as noted by > Nhat Pham). > > We can find these counters from /proc/vmstat (counters for the whole > system) and memcg's memory.stat (counters for the interested memcg). > > For example: > > $ grep -E 'swpin_zero|swpout_zero' /proc/vmstat > swpin_zero 1648 > swpout_zero 33536 > > $ grep -E 'swpin_zero|swpout_zero' /sys/fs/cgroup/system.slice/memory.sta= t > swpin_zero 3905 > swpout_zero 3985 > LGTM FWIW, so I'll leave my review tag here: Reviewed-by: Nhat Pham Too many emails in this thread, but my opinions is: 1. A fix tag is appropriate. It's not a kernel bug per se, but it's incredibly confusing, and can potentially throw off user space agents who rely on the rate of change of these counters as signals. 2. I do think we should use a separate set of counters for this optimization. No strong opinions regarding combining this with the zswap counters, but it can get confusing for users when they enable/disable zswap. If we are to combine, I'd be much more comfortable if we have a generic name, like the one David suggested in v1 ("swpin_skip" / "swpout_skip"). This would still require some API change tho, so not sure if this is the best approach? :) It would also be appropriate if we bring back the same-filled optimization (which should be doable in the swap ID world, but I digress).