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Tue, 28 Mar 2023 15:03:19 -0700 (PDT) MIME-Version: 1.0 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> In-Reply-To: From: Yosry Ahmed Date: Tue, 28 Mar 2023 15:02:43 -0700 Message-ID: Subject: Re: [LSF/MM/BPF TOPIC] Swap Abstraction / Native Zswap To: Chris Li Cc: "Huang, Ying" , lsf-pc@lists.linux-foundation.org, Johannes Weiner , 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 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: iafm588dgwhape5qfbbb7mfx67foyuu3 X-Rspamd-Queue-Id: AF142A0024 X-HE-Tag: 1680041001-787283 X-HE-Meta: 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 J4hIDq0V /TXHA77MU8OP8BOBd/CMd+CHeeFLRs5fAdid1mRp7riESJnY8PjKJK+XD0kjLbpPvp24H7YltwDIej1qqQeVIW76P4ewJDOvZ0jmUua2sJZXIOpGaDHPy9q5fLdcZiJqbq6wgQpN5YjsGL+Ub8SqlfRj8h0F/v0pJtW8mDNt6qvAcmrdKF08jpOTC5pqfGyctXsQHn8Pv/762YJAVmUFLfQ8Zw1Gh4n1rnR0SbKGMB+T1H5TeyoDn09dS9+Hfou9QIEagaM+1HCEZZoRP2iO++DsiF//QIjJ0BUCQA6NJO/89MfVs0aDHqJDHzxFsRQ6uACpShNhC+7q56g8= 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 3:01=E2=80=AFPM Chris Li wrote: > > On Tue, Mar 28, 2023 at 02:44:27PM -0700, Yosry Ahmed wrote: > > > Your swap descriptor will be using one swp_entry_t, which get from th= e PTE > > > to lookup, right? That is the swap entry I am talking about. You just > > > substitute zswap swap entry with the swap descriptor swap entry. > > > You still need to allocate from the free swap entry space at least on= ce. > > > > Oh, you mean the swap ID space. We just need to find an unused ID, we > > can simply use an allocating xarray > > (https://docs.kernel.org/core-api/xarray.html#allocating-xarrays). > > This is simpler than keeping track of swap slots in a swapfile. > > Ah I see. That makes sense. Thanks for explaining it to me. > > The real block swap device will still need to scan the swap_map > to find an empty space to write the page. Yes, exactly. It's a tradeoff, and I think as long as whatever we decide can be considered as a step towards the right direction it should be fine. > > Chris > >