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t=1680038553; bh=fSu26aTs67veI5jA4pAMfdIg0PkCCw/FLczG3Qkntrk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=dCSn9w4Ul/QEvTpkp2zVq2fLTx0MNhHgmlCSlKbriAoawWvYpL4EdHwZx6h1cPXr3 egj5AP/pr0+Bu8EtIiuIhkoErUe2WmZrUsWeEVq3dPiRoIA5FWOVyN68o9CRDIrCjk RF3Fa8ci2BrQQGk3gBUC8d2jNFw5Fe/t0kEDA6jmjxjy5UyiROCR/PazNrURgqKkoS MH0KZ/+jvlbtqNH7hZ+QbqPfZkNFOeiXRbRvuBaTU5R+gfYVbVekScBJnMgyeuzDoo q8/LHRG2P2Kkyft4q0Ak0vPbi2HWT9fdv+xATbzhEcBcUHI8BeKTwPm3okbb4Qz1Kh BSksnRFl6EysA== Date: Tue, 28 Mar 2023 14:22:31 -0700 From: Chris Li To: Yosry Ahmed Cc: Johannes Weiner , "Huang, Ying" , lsf-pc@lists.linux-foundation.org, Linux-MM , Michal Hocko , Shakeel Butt , David Rientjes , Hugh Dickins , Seth Jennings , Dan Streetman , Vitaly Wool , Yang Shi , Peter Xu , Minchan Kim , Andrew Morton , Aneesh Kumar K V , Michal Hocko , Wei Xu Subject: Re: [LSF/MM/BPF TOPIC] Swap Abstraction / Native Zswap Message-ID: References: <87edpbq96g.fsf@yhuang6-desk2.ccr.corp.intel.com> <87jzz1pfb3.fsf@yhuang6-desk2.ccr.corp.intel.com> <87fs9ppdhz.fsf@yhuang6-desk2.ccr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 436A420006 X-Rspam-User: X-Stat-Signature: ae4kfzee88ag3ow94k7ktkmdb3jjj4ze X-HE-Tag: 1680038556-491782 X-HE-Meta: U2FsdGVkX19r5Rnb6fb3MTMevh4dW3w38nUBxmE/Y36pv/+eUhg8XkeiRRrny+vF2uKVkFpUqHeIbZACBwkVlLnKDHeQYettpfr/jwiZ8AJPPixZh+zL5/IANjww0FYDk/QL73PRF5WUGd4Opn6VYiO4qtNL81Scc1LZD97UICQwkm8dr7iU7Oj2MDhnoaMfSmI4xLIfqApj6lySoNPiqnZWW0dKkOUJFgkwRwo9sEFaSwlAccNZY8y19w25OeUBSp2YSbpMCa44dLjWxKtnnX3778h+bbw36SCWvHmmSTOlBNoSsm2fcme4RCHysXjM75Ff1GEYtx4g+rvv3SBcxueWTGcHBuh2kB98MYTUyPnymqZL/oZYiLGca9rfeGJvxuThgGgXrH3Dlthu7ew3Pi93WK5GDzwrXPuoHHeO6W6oWnQLvrll2rLueJN8kYt0iFI4hVbtiqWzKY1k/KFae/DWVRq+rWlGACKcO7dFwM158GwEwCcm+9MqjYCaWLuK2lMzDCdOuRY+atwnNRBRrtufpFOJO+XaHi4HMj6aIexqz+ySFQ3ZidC9cUdQ2+6berUq5PdOmXOX43eWQ6gkl26RZuxFDJ2m6ztSFhMNcb6ZCefBkTGaLWpw6PXxuyEfgzIFANt2QB7pR6olsuHXXxv8qdxvCpExwlMJnRosMK1/n1lfBv0iOux1KMbins0zlDzUAPWHs6VQEm0b6YvVBulI2HS1SKO6FRQMK+/VDO5stPTvbozftkswT+bw50hAt3k/DzGrIfC1GuvFobTpSTgVHsjEOebMj/mDSyIESU0i5EdRj7nPzC0Jkp/0gaaHMloOyeMhS4yarjBQ4hfuXtDkVzfnf4ZdBRwRVOZqBkrE4cjLEtLdP6w4qQ7R4YK70ui1iRIhUw67MqzaO4+FTEFd3xix1aGiSFDUo7I0teN2dEp2rO94/P073yafxZuQ3usd5BWHl0Ob8Mdvtcm GJpqf7vi wXgCXIyrGdAXLbuusQOjo3Mog2EEO1Q/dtXlIIuUcy8odHYkV/uYPPUz/5QYX/aSTF8XHP8bOO055JuJ2p5eb+eeEteQKQV/QKmy/FMTky/Wi/5XwsQS1tld7OEKYUTrLC/PV3l0Kc+BGLu0q3wIW1zcm8a7scM1YF2lqE7ubZjBlfmtaKILWs+agd713aDUsHOQT 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: On Tue, Mar 28, 2023 at 12:59:55PM -0700, Yosry Ahmed wrote: > > So it wouldn't be my first preference. But it sounds workable. > > If we settle on this as a first step, perhaps to avoid any ABI changes Turn on zswap without a real swapfile is user space visible change. Some small change is unavoidable, ABI or not. > we can have the kernel create a virtual swap device for zswap if it is > enabled, without userspace interfering or having to do swapon on a > sparse swapfile like we do today with ghost swapfiles at Google. We > can then implement indirection logic that only supports moving pages > between swap devices -- and perhaps only restrict it to only support > the virtual zswap swap device as a top tier initially. One more things to consider is that, Google use more than one ghost swapfiles for zswap due to scalability. There might be scalability implication if there can be only one zswap device. Chris