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Thu, 12 Oct 2023 07:22:04 -0700 (PDT) Received: from localhost ([2620:10d:c091:400::5:66a6]) by smtp.gmail.com with ESMTPSA id jy20-20020a0562142b5400b0065d05c8bb5dsm464815qvb.64.2023.10.12.07.22.04 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 12 Oct 2023 07:22:04 -0700 (PDT) Date: Thu, 12 Oct 2023 10:22:03 -0400 From: Johannes Weiner To: =?utf-8?B?6LS65Lit5Z2k?= Cc: Nhat Pham , akpm@linux-foundation.org, yosryahmed@google.com, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [External] Re: [RFC PATCH] zswap: add writeback_time_threshold interface to shrink zswap pool Message-ID: <20231012142203.GB470544@cmpxchg.org> References: <20231011051117.2289518-1-hezhongkun.hzk@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: D8F534002E X-Stat-Signature: yn76mopcxmw1x867moqzmcpc1dqra4ic X-Rspam-User: X-HE-Tag: 1697120525-67454 X-HE-Meta: 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 yvgnxPXs 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000175, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Thu, Oct 12, 2023 at 10:13:16PM +0800, 贺中坤 wrote: > Hi Nhat, thanks for your detailed reply. > > > We're currently trying to solve this exact problem. Our approach is to > > add a shrinker that automatically shrinks the size of the zswap pool: > > > > https://lore.kernel.org/lkml/20230919171447.2712746-1-nphamcs@gmail.com/ > > > > It is triggered on memory-pressure, and can perform reclaim in a > > workload-specific manner. > > > > I'm currently working on v3 of this patch series, but in the meantime, > > could you take a look and see if it will address your issues as well? > > > > Comments and suggestions are always welcome, of course :) > > > > Thanks, I've seen both patches. But we hope to be able to reclaim memory > in advance, regardless of memory pressure, like memory.reclaim in memcg, > so we can offload memory in different tiers. Can you use memory.reclaim itself for that? With Nhat's shrinker, it should move the whole pipeline (LRU -> zswap -> swap). > Thanks for your review，we should update the store time when it was loaded. > But it confused me, there are two copies of the same page in memory > (compressed and uncompressed) after faulting in a page from zswap if > 'zswap_exclusive_loads_enabled' was disabled. I didn't notice any difference > when turning that option on or off because the frontswap_ops has been removed > and there is no frontswap_map anymore. Sorry, am I missing something? In many instances, swapins already free the swap slot through the generic swap code (see should_try_to_free_swap()). It matters for shared pages, or for swapcaching read-only data when swap isn't full - it could be that isn't the case in your tests.