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AJvYcCVHEClYUHbu8EEsRs0uj7eYmvzSLgubgUmNHqvEYA9WxnuE5Kg62XBA4yCJ/pMi+ez/48uLUrkQVA==@kvack.org X-Gm-Message-State: AOJu0YyeBz5Wa0DAW505IVg5ryKiOZQHAypuk8TqeJzpygw+lRw6tH/f Ofh7kV3kHh1l0FoWTTDmb0tybzT0U/72xi2r5uSx/Lle6so3uaC/KdESv58KNx++cZQsmWntLF+ 0QZPPrlxUWNUF2rf4EsTT5iLvf04= X-Google-Smtp-Source: AGHT+IHXK9nQ9QtWcoKL6O6kNc6crcuq/kVTfgAMJ5oBd7mzsQSHHnIINf8SoFEiOfTqM7iDoA4H0nwzBGX/oWz+iIo= X-Received: by 2002:a05:6102:1609:b0:4a4:8651:3c46 with SMTP id ada2fe7eead31-4aada3ab046mr476016137.18.1730975129947; Thu, 07 Nov 2024 02:25:29 -0800 (PST) MIME-Version: 1.0 References: <20240327214816.31191-3-21cnbao@gmail.com> <20241021232852.4061-1-21cnbao@gmail.com> In-Reply-To: From: Barry Song <21cnbao@gmail.com> Date: Thu, 7 Nov 2024 23:25:18 +1300 Message-ID: Subject: Re: [PATCH RFC 2/2] zram: support compression at the granularity of multi-pages To: Usama Arif Cc: akpm@linux-foundation.org, axboe@kernel.dk, chrisl@kernel.org, corbet@lwn.net, david@redhat.com, kanchana.p.sridhar@intel.com, kasong@tencent.com, linux-block@vger.kernel.org, linux-mm@kvack.org, minchan@kernel.org, nphamcs@gmail.com, senozhatsky@chromium.org, surenb@google.com, terrelln@fb.com, v-songbaohua@oppo.com, wajdi.k.feghali@intel.com, willy@infradead.org, ying.huang@intel.com, yosryahmed@google.com, yuzhao@google.com, zhengtangquan@oppo.com, zhouchengming@bytedance.com, bala.seshasayee@linux.intel.com, Johannes Weiner Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Queue-Id: 1E07A180011 X-Rspamd-Server: rspam11 X-Stat-Signature: pz5t3xgs55ft9n6nej38uwun66g84hco X-HE-Tag: 1730975127-23454 X-HE-Meta: U2FsdGVkX1+Z4RgQRh8d0jlvIr4BfTMsvIsI8HrJmXo/8fJaoMUFMThcf3g2fVq8nYmtSSx0vlP9wwlpbUY+fUas26MtmGE2Y3xf9PSWm0azY4Cyr8CLYeEr8zlcLY3x9jn6NB6XmVLhrhbHisXxSOrHMxktvf4H+Kacfwy+qcMGVulmihVb3BAu5Fj7vrr5rD1wXnanctRr6nI3qajuEPB5SdRFfCf/hKj9Z1MfEJp9jMA6Cx7C0R3xOGXXGC9wXbxenfP03rzePCwogYtCEJU7AH70wH8lXC/C0sYsAMHsD0Us8+hAMOWs+InGZ/tj5pTfzQjOoRjU6BAy2KP6WVld8g81Ls4HR/cZZ7TDcRGa9gm4oCr4y0q1Y9ieLDV0gvl5oz2w+kNAoN3d4/T/LYMNb7VhVLlf9QOfJEDiRUXR3beCxWuNWiVKvloi42xJS8KBEhVOEYS72lK4pooAPD1BcRhwS1c26ifCfBhVvVt3ZX2O6Lno8NjPks2J+VxhzMCpZamN91iGnSWu3h/ppNu6I5tVKYheVEgeYRp2OP5jwnbj8DjxcZxiiXecucPPA9y2goXqqXHbLAs7fK3k764lAmdvEcZBdST3G6GVJY4+PCY8JUKNrPxodnolBSXlPvXkT8Pp/7TfoVVcHg7ZCjOMmsaonRgARhnvkLppqHEw5bNbSD9Z+vTmujiRSeul/xNJDelwcw4LNAzGxbJKLobxDYQ12EnkDKV6x1GM4r+3YtxXGUOSL1YH1id3rPhqUfQ3NcR9P8dW+UWsrhGGYMRPTzj/r18TeY4E0EA3xCsyqQamxfz/DBgleNkHnfPupC0LPv6VfPgZNJR8HM+QokMEbrIeqzIhSsIzHg5/ijDpGAaBwCaks244lTFitSCtpFPc6FFBSaORwewPjb6b5peNOmMA9ZZvqQfBvA1j0YZC/uRPuTEU1N5bRtiigupcUXs0M49lYcEZxt4F9q/ c+ZRaEf6 6TZciEh/3LXdsotLGJtm9mJEaeQX81q6CmysmjtZGq79WTHCYsXIY26gHPOQv+K6s0pXU/Z97B2BCWAR9lwQrKmmeMUVaS+xVA3RLGlToE8kLU/XTldpQrkPqNH051ftRE4qP9YVJLJ58ObIFhgyNlaUqno/1DcL6YMnPW1HtLBVdKANNbq+fXLuPyKqCfE33H4sH3dTS3tHPo3eY3dA+UD6Q2ABEgCzYGV5V/KL1C72rpgolzao+LKwKp6yWbg3ugN0RucqXdEoup5l4OUdHqc0mfjAydXdrnk+r6wsIU8XSJ0tn5kJUl4wAngIoP7t40Tq/Xhf5DA/uUtIUkmw8cQnIP3/BtD75Bddx6zt7D+g3Ls6vgpaQ1ypJMw== 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 Thu, Nov 7, 2024 at 5:23=E2=80=AFAM Usama Arif = wrote: > > > > On 22/10/2024 00:28, Barry Song wrote: > >> From: Tangquan Zheng > >> > >> +static int zram_bvec_write_multi_pages(struct zram *zram, struct bio_= vec *bvec, > >> + u32 index, int offset, struct bio *bio) > >> +{ > >> + if (is_multi_pages_partial_io(bvec)) > >> + return zram_bvec_write_multi_pages_partial(zram, bvec, in= dex, offset, bio); > >> + return zram_write_page(zram, bvec->bv_page, index); > >> +} > >> + > > Hi Barry, > > I started reviewing this series just to get a better idea if we can do so= mething > similar for zswap. I haven't looked at zram code before so this might be = a basic > question: > How would you end up in zram_bvec_write_multi_pages_partial if using zram= for swap? Hi Usama, There=E2=80=99s a corner case where, for instance, a 32KiB mTHP is swapped out. Then, if userspace performs a MADV_DONTNEED on the 0~16KiB portion of this original mTHP, it now consists of 8 swap entries(mTHP has been released and unmapped). With swap0-swap3 released due to DONTNEED, they become available for reallocation, and other folios may be swapped out to those entries. Then it is a combination of the new smaller folios with the original 32KiB mTHP. > > We only swapout whole folios. If ZCOMP_MULTI_PAGES_SIZE=3D64K, any folio = smaller > than 64K will end up in zram_bio_write_page. Folios greater than or equal= to 64K > would be dispatched by zram_bio_write_multi_pages to zram_bvec_write_mult= i_pages > in 64K chunks. So for e.g. 128K folio would end up calling zram_bvec_writ= e_multi_pages > twice. In v2, I changed the default order to 2, allowing all anonymous mTHP to benefit from this feature. > > Or is this for the case when you are using zram not for swap? In that cas= e, I probably > dont need to consider zram_bvec_write_multi_pages_partial write case for = zswap. > > Thanks, > Usama Thanks barry