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]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 45AC2C98302 for ; Tue, 22 Sep 2026 17:15:37 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 499FB6B00AD; Tue, 22 Sep 2026 13:15:36 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 470CA6B00AE; Tue, 22 Sep 2026 13:15:36 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 387446B00AF; Tue, 22 Sep 2026 13:15:36 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id 022826B00AD for ; Tue, 22 Sep 2026 13:15:35 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay05.hostedemail.com (Postfix) with ESMTP id 80D554056D for ; Tue, 22 Sep 2026 17:15:35 +0000 (UTC) X-FDA: 85242049830.20.5210293 Received: from shelob.surriel.com (shelob.surriel.com [96.67.55.147]) by imf13.hostedemail.com (Postfix) with ESMTP id C868B2000D for ; Tue, 22 Sep 2026 17:15:33 +0000 (UTC) Authentication-Results: imf13.hostedemail.com; dkim=pass header.d=surriel.com header.s=mail header.b="hqU0CB y"; dmarc=pass (policy=quarantine) header.from=surriel.com; spf=pass (imf13.hostedemail.com: domain of riel@surriel.com designates 96.67.55.147 as permitted sender) smtp.mailfrom=riel@surriel.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790097333; 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=aIvSiXa3+TYx7bi3V5dw42Ue3KZMD0siULIfE/dvEQI=; b=Dvn9FByi6tHMBFSONkCFNNvv7VBRwm0lr35O0j+XoxGyTgQX7HhnICotiSAOC+dEgCKuHm BJ2OOxvyYXeEISuNPbXixOBJbAJcjKh5YWNFNYRScnPLUiKsjmp6lYv53ohf+GroheLfkB XdJzUBvaeE0rhqSQeWma3vPzBm6l5/o= ARC-Authentication-Results: i=1; imf13.hostedemail.com; dkim=pass header.d=surriel.com header.s=mail header.b="hqU0CB y"; dmarc=pass (policy=quarantine) header.from=surriel.com; spf=pass (imf13.hostedemail.com: domain of riel@surriel.com designates 96.67.55.147 as permitted sender) smtp.mailfrom=riel@surriel.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790097333; b=MGt9ck7EiveHGKOxm7UH22QwFhqWVqXUj8alBvToR2ZMElsWf95blNbm7xFuiijIiYS+Fg TJUCAFEjUcA9gcIZ5cBobrZt7/8qo3AOTxnNcrFz40Rp/gRt4ifdy/64vIvodo47VEvQt/ q6r7MUSE7ljkPjRuqSCCihZ2lUEpsO4= DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=surriel.com ; s=mail; h=MIME-Version:Content-Transfer-Encoding:Content-Type:References: In-Reply-To:Date:Cc:To:From:Subject:Message-ID:Sender:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID; bh=aIvSiXa3+TYx7bi3V5dw42Ue3KZMD0siULIfE/dvEQI=; b=hqU0CB ySEEvdprfEWb4xkQGlSn5w5HAV/81c1nWMKXoCFV55o1L37ZqwMu/yLZKBSdEWulJow0fgW1ASBzY akE5fpIwK2d3Cm5JM6y0v9JOjic5dzKmjiu8B2tTMnwD+ANo53TYLzNHPueeDA2khb7BSrcIZNizZ tVYFnVzuAMxjRvQKEl0PTqx8IsS8zAlRlk0pEishPQZnfVlkn3R3bYE8gAE2x7H1uZQBnpAzAj32o sAQPZjjvtrjXzWcXej3uU34edcyi+cS1G5MWFUQmCnjZHQyMd2ZAcTrReEFqoovKkqMq68UMJdJ9z aSPmsCJSow5ChZrzopeDLdjz5ITQ==; Received: from [2601:18c:8100:a0e0:5a47:caff:fe78:8708] by shelob.surriel.com with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.99.5) (envelope-from ) id 1x944f-00000001udR-0YDT; Tue, 22 Sep 2026 17:14:33 +0000 Message-ID: Subject: Re: Path forward for Virtualized Swap? From: Rik van Riel To: Chris Li , Gregory Price Cc: Johannes Weiner , Baoquan He , Nhat Pham , Kairui Song , Michal Hocko , Roman Gushchin , Shakeel Butt , Yosry Ahmed , David Hildenbrand , Muchun Song , Kemeng Shi , Barry Song , YoungJun Park , Chengming Zhou , "Lorenzo Stoakes (Oracle)" , "Liam R. Howlett" , "Vlastimil Babka (SUSE)" , Mike Rapoport , Suren =?UTF-8?Q?Baghdasaryan=EF=BF=BC?= , Qi Zheng , Axel Rasmussen , Yuanchu Xie , Wei Xu , Wenchao Hao , Jonathan Corbet , Hugh Dickins , Baolin Wang , Tejun Heo , Michal =?ISO-8859-1?Q?Koutn=FD?= , Shuah Khan , Kunwu Chan , Meta kernel team , Linux Memory Management List , Linux Kernel Mailing List , linux-doc@vger.kernel.org, "open list:CONTROL GROUP - MEMORY RESOURCE CONTROLLER (MEMCG)" , Andrew Morton , Kairui Song , Joshua Hahn Date: Tue, 22 Sep 2026 13:14:31 -0400 In-Reply-To: References: Autocrypt: addr=riel@surriel.com; prefer-encrypt=mutual; keydata=mQENBFIt3aUBCADCK0LicyCYyMa0E1lodCDUBf6G+6C5UXKG1jEYwQu49cc/gUBTTk33A eo2hjn4JinVaPF3zfZprnKMEGGv4dHvEOCPWiNhlz5RtqH3SKJllq2dpeMS9RqbMvDA36rlJIIo47 Z/nl6IA8MDhSqyqdnTY8z7LnQHqq16jAqwo7Ll9qALXz4yG1ZdSCmo80VPetBZZPw7WMjo+1hByv/ lvdFnLfiQ52tayuuC1r9x2qZ/SYWd2M4p/f5CLmvG9UcnkbYFsKWz8bwOBWKg1PQcaYHLx06sHGdY dIDaeVvkIfMFwAprSo5EFU+aes2VB2ZjugOTbkkW2aPSWTRsBhPHhV6dABEBAAG0HlJpayB2YW4gU mllbCA8cmllbEByZWRoYXQuY29tPokBHwQwAQIACQUCW5LcVgIdIAAKCRDOed6ShMTeg05SB/986o gEgdq4byrtaBQKFg5LWfd8e+h+QzLOg/T8mSS3dJzFXe5JBOfvYg7Bj47xXi9I5sM+I9Lu9+1XVb/ r2rGJrU1DwA09TnmyFtK76bgMF0sBEh1ECILYNQTEIemzNFwOWLZZlEhZFRJsZyX+mtEp/WQIygHV WjwuP69VJw+fPQvLOGn4j8W9QXuvhha7u1QJ7mYx4dLGHrZlHdwDsqpvWsW+3rsIqs1BBe5/Itz9o 6y9gLNtQzwmSDioV8KhF85VmYInslhv5tUtMEppfdTLyX4SUKh8ftNIVmH9mXyRCZclSoa6IMd635 Jq1Pj2/Lp64tOzSvN5Y9zaiCc5FucXtB9SaWsgdmFuIFJpZWwgPHJpZWxAc3VycmllbC5jb20+iQE +BBMBAgAoBQJSLd2lAhsjBQkSzAMABgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDOed6ShMTe g4PpB/0ZivKYFt0LaB22ssWUrBoeNWCP1NY/lkq2QbPhR3agLB7ZXI97PF2z/5QD9Fuy/FD/jddPx KRTvFCtHcEzTOcFjBmf52uqgt3U40H9GM++0IM0yHusd9EzlaWsbp09vsAV2DwdqS69x9RPbvE/Ne fO5subhocH76okcF/aQiQ+oj2j6LJZGBJBVigOHg+4zyzdDgKM+jp0bvDI51KQ4XfxV593OhvkS3z 3FPx0CE7l62WhWrieHyBblqvkTYgJ6dq4bsYpqxxGJOkQ47WpEUx6onH+rImWmPJbSYGhwBzTo0Mm G1Nb1qGPG+mTrSmJjDRxrwf1zjmYqQreWVSFEt26tBpSaWsgdmFuIFJpZWwgPHJpZWxAZmIuY29tP okBPgQTAQIAKAUCW5LbiAIbIwUJEswDAAYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQznneko TE3oOUEQgAsrGxjTC1bGtZyuvyQPcXclap11Ogib6rQywGYu6/Mnkbd6hbyY3wpdyQii/cas2S44N cQj8HkGv91JLVE24/Wt0gITPCH3rLVJJDGQxprHTVDs1t1RAbsbp0XTksZPCNWDGYIBo2aHDwErhI omYQ0Xluo1WBtH/UmHgirHvclsou1Ks9jyTxiPyUKRfae7GNOFiX99+ZlB27P3t8CjtSO831Ij0Ip QrfooZ21YVlUKw0Wy6Ll8EyefyrEYSh8KTm8dQj4O7xxvdg865TLeLpho5PwDRF+/mR3qi8CdGbkE c4pYZQO8UDXUN4S+pe0aTeTqlYw8rRHWF9TnvtpcNzZw== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) MIME-Version: 1.0 X-Rspamd-Queue-Id: C868B2000D X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: tzi47uzf8ytfwkee6rxhqww74o1mcxh8 X-HE-Tag: 1790097333-497448 X-HE-Meta: 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 mMYuaXys xjWYry+0l9kEJ8gT2lkN3b9H+AtHmXQ20jsuAO6FpqaKFtjAP1aLBrxOpwBm96KP5ev379qxBwmdIc+U3WF73wIJ1OI+O7HqInLbtBJ67q8VYz54XAPqEJuaNhLF/BO+E9NeDsBOpUerfDqKYZdqAg5SwfH0nZhU4Z6EBzSGh1hzV6tsKUqwjckvxDcGIv4XDjio+J7B7nVlww3md87oMA9o8aF4zQwLuiwIeTtehtmOxWtlmtDjGu5gfB+kwCMEq8T7xntVCukZcZNaZV1iFIkLabWhuG8jqXxYmb7seFuRcgQnJRuGb3HwUetY2EM46/tYZ0ovDKTpHC406nTYUmcSXBAg0AkI9Zj/jsNG3ydX8dsc5JJYlJTnsE267TDKDKiMTFrcD/sj96A1vO/75ivAQ2Ku6T9gBwvriyLUQpbNcsPhk9AU7RrT394scQO8zmkRqJdTlXJdfbuo= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, 2026-09-21 at 06:11 -1000, Chris Li wrote: > On Mon, Sep 21, 2026 at 2:53=E2=80=AFAM Gregory Price > wrote: >=20 > >=20 > > You can't know the compressibility of memory until after you > > compress > > it, and requiring a user to predict the future by forcing them to > > limit > > the total amount of workload compressibility does not scale with > > the > > number of workloads of variable compressibility of data. >=20 > You likely just need to pull a SQL query on your fleet to get that > number. This feature is not being developed for just one user. It has to work for everybody. >=20 > > That should tell you that your model of reasoning about this issue > > is > > ill-suited to address the problem. >=20 > That is what I'm suspecting. Nobody in a sane mind would want to > zswap > 100% of the RAM and maintain reasonable SLO. >=20 It could make a lot of sense to have some default limit upstream, that says the zswap pool is not allowed to take more than half of memory, because at that point the compressed content will be crowding other things out of memory. That seems like the kind of limit that is large enough that very few people will run into it,=C2=A0 while also being small enough to prevent actual corner case trouble. --=20 All Rights Reversed.