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Tue, 26 Nov 2024 21:04:53 -0800 (PST) Received: from google.com ([2401:fa00:8f:203:cda8:c605:6e79:8b60]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-7fbcc422d0bsm8262535a12.84.2024.11.26.21.04.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 26 Nov 2024 21:04:52 -0800 (PST) Date: Wed, 27 Nov 2024 14:04:45 +0900 From: Sergey Senozhatsky To: Barry Song <21cnbao@gmail.com> Cc: Sergey Senozhatsky , akpm@linux-foundation.org, linux-mm@kvack.org, axboe@kernel.dk, bala.seshasayee@linux.intel.com, chrisl@kernel.org, david@redhat.com, hannes@cmpxchg.org, kanchana.p.sridhar@intel.com, kasong@tencent.com, linux-block@vger.kernel.org, minchan@kernel.org, nphamcs@gmail.com, ryan.roberts@arm.com, surenb@google.com, terrelln@fb.com, usamaarif642@gmail.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 Subject: Re: [PATCH RFC v3 0/4] mTHP-friendly compression in zsmalloc and zram based on multi-pages Message-ID: <20241127050445.GG440697@google.com> References: <20241121222521.83458-1-21cnbao@gmail.com> <20241126050917.GC440697@google.com> <20241126105258.GE440697@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Queue-Id: 301E540006 X-Rspamd-Server: rspam12 X-Stat-Signature: n745tk43xdihm565tfzchse9aokrjtdi X-Rspam-User: X-HE-Tag: 1732683890-19936 X-HE-Meta: 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 49VUOCs9 xT2qRb7U7OxyO+rNgOpWDypljwQvSChCncfxGkifp57mBsFSincDndMyAFLLMtuPv2Rn3o8HB9TNetoAJh/XLf59x/OFpEJUh+qkQ5wT1rZVl+P5jXtlEJyz36Hb/qKjpyvkkhM3xipblRZokJ3mLTfbw9A9dzMNluZ0wepHzPFrQ1d4rIPOSRMMdjlrIgDGCWaI4NWQ/Pk3yQ1QTYhop9YR7St4NIkPZ2M1onqxwkhTbTGKS1mvO6IKkNNi2rl/B1LlAP6JY62GgSTb9mP4ljkGx04gUfkRVJtCmWiCpqYcDnOEYbenMK1BmPfWEZ2EX84eQ6b0zB0/dzjyvOssCP1fbGDko5Kl6nk+SbRuDCjXM7FTPfNKuadZSeduLLc71B1+OGsGJE1CQx9Q= X-Bogosity: Ham, tests=bogofilter, spamicity=0.004984, 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 (24/11/27 09:31), Barry Song wrote: > On Tue, Nov 26, 2024 at 11:53 PM Sergey Senozhatsky > wrote: > > > > On (24/11/26 14:09), Sergey Senozhatsky wrote: > > > > swap-out time(ms) 68711 49908 > > > > swap-in time(ms) 30687 20685 > > > > compression ratio 20.49% 16.9% > > > > I'm also sort of curious if you'd use zstd with pre-trained user > > dictionary [1] (e.g. based on a dump of your swap-file under most > > common workloads) would it give you desired compression ratio > > improvements (on current zram, that does single page compression). > > > > [1] https://github.com/facebook/zstd?tab=readme-ov-file#the-case-for-small-data-compression > > Not yet, but it might be worth trying. A key difference between servers and > Android phones is that phones have millions of different applications > downloaded from the Google Play Store or other sources. Maybe yes maybe not, I don't know. It could be that that 99% of users use the same 1% apps out of those millions. > In this case, would using a dictionary be a feasible approach? Apologies > if my question seems too naive. It's a good question, and there is probably only one way to answer it - through experiments, it's data dependent, so it's case-by-case. > On the other hand, the advantage of a pre-trained user dictionary > doesn't outweigh the benefits of large block compression? Can’t both > be used together? Well, so far the approach has many unmeasured unknowns and corner cases, I don't think I personally even understand all of them to begin with. Not sure if I have a way to measure and analyze, that mTHP swapout seems like a relatively new thing and it also seems that you are still fixing some of its issues/shortcomings.