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Thu, 15 Jun 2023 20:44:12 -0700 (PDT) MIME-Version: 1.0 References: <20230615034830.1361853-1-hezhongkun.hzk@bytedance.com> <3f54542e-235b-8456-f13f-786d21c6c14f@redhat.com> <290d79bb-b1a6-3146-76a7-9938829e6ebe@redhat.com> In-Reply-To: <290d79bb-b1a6-3146-76a7-9938829e6ebe@redhat.com> From: =?UTF-8?B?6LS65Lit5Z2k?= Date: Fri, 16 Jun 2023 11:44:01 +0800 Message-ID: Subject: Re: [External] Re: [RFC PATCH 1/3] zram: charge the compressed RAM to the page's memcgroup To: David Hildenbrand Cc: minchan@kernel.org, senozhatsky@chromium.org, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: BF9A3140003 X-Rspam-User: X-Stat-Signature: iun51b1ukt91h4wcwuzp68435uaub9mg X-Rspamd-Server: rspam03 X-HE-Tag: 1686887053-913098 X-HE-Meta: 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 TSl8i8Bq WyZ7S+NTb+xKwdpfsfuz39sf7BbQRfvyZi6wWMOJYU39vxXIkHCE9wuVLn5iq6zhTg538vPjgGTO2FWMW0Hen6/XgRppqjDUhSQbD+cqGKv9NzkbZKSmyLOtbcY474iToQFENf9CI8iF3liuzP2+6CS2A2EBl16O9SPGcAUMpUCtfmkc6R+if+eD8YJDBthO5rTF7zL4/kUxe+pxB7LHIk8Xe6XT3Cs1JHfMPbhLSEWJ5L2aaiSS3y2CD6WTFrVIdThju 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: > > Yes. But just to stress again, one issue I see is that if there is a > page in the BIO that is not charged, you cannot charge the compressed pag= e. I got it. Thanks. > > Assume you have some FS on that zram block device and you want to make > sure it gets properly charged to whoever is reading/writing a file on > that filesystem. (imagine something like a compress shmem) > > If a user (or the filesystem?) can trigger a BIO that has an uncharged > page in it, it would not get charged accordingly. > > The "easy" reproducer would have been O_DIRECT write() using the shared > zeropage, but zram_write_page() is smart enough to optimize for that > case (page_same_filled()). :) Ok, I will try it. > > Maybe I'm over-thinking this (well, the we do have partial I/O support, > so something seems to be able to trigger such cases), and it would be > great if someone with more FS->BIO experience could comment. > > I'll note that this is fundamentally different to zswap, because with > zswap you don't get arbitrary BIOs, you get an anon or shmem page (that > should be charged). > Hi David=EF=BC=8C I know your concern and I will try to find the uncharged = case. > -- > Cheers, > > David / dhildenb >