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h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=srFtzH7bBResBMSJzOLKtKeNVfecDDDsflVsoADT8dc4QsaV+hDy6JYa0fDT3rdw/ /+qA5icI2kfJuHuRz5ObGU1BkO3SSZ/8uf04gOr1HhrVSNw56ay0NTKyE4P4LhYrmL r7yl0odutcZCfTxsazBgPYAlK91jHn3altwqgw78= Date: Fri, 8 Dec 2023 11:57:29 -0800 From: Andrew Morton To: Nhat Pham Cc: tj@kernel.org, lizefan.x@bytedance.com, hannes@cmpxchg.org, cerasuolodomenico@gmail.com, yosryahmed@google.com, sjenning@redhat.com, ddstreet@ieee.org, vitaly.wool@konsulko.com, mhocko@kernel.org, roman.gushchin@linux.dev, shakeelb@google.com, muchun.song@linux.dev, hughd@google.com, corbet@lwn.net, konrad.wilk@oracle.com, senozhatsky@chromium.org, rppt@kernel.org, linux-mm@kvack.org, kernel-team@meta.com, linux-kernel@vger.kernel.org, linux-doc@vger.kernel.org, david@ixit.cz, chrisl@kernel.org Subject: Re: [PATCH v6] zswap: memcontrol: implement zswap writeback disabling Message-Id: <20231208115729.acb78677883c13c2c62a29d3@linux-foundation.org> In-Reply-To: References: <20231207192406.3809579-1-nphamcs@gmail.com> <20231207141142.307745be167d044b0eec1b42@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: BB30D100023 X-Stat-Signature: 1hxb1xfbs164ekfwx4zjddw76kecngic X-Rspam-User: X-HE-Tag: 1702065452-687506 X-HE-Meta: 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 aYeZFQNw NsCxUpswNiNoXcAH1Pnmg+UFn13eh21CFhNjHUbcJjiTqplbSOiGcHN6pW6xy7Y3/uUyJ1xTNOStZJBU7sdukcU8I2R8laxNSOYuHTUxL89FFb4Ab5ZtkQ3YHdupY888qELjXlgiwyAXerJWerbIZhQvKqH1wOGpP7swVJfy7QzjE3YBTT+L7NfBCJRCJPWwBpeT0jAd6WW1WfiuDIAVqi2ufB74IWX+Xkezbu1MGqHJ2vagux3aB5rw8jaEPiwReHiHO 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, 7 Dec 2023 16:42:59 -0800 Nhat Pham wrote: > > > > Also, it would be quite helpful of the changelog were to give us some > > idea of how important this tunable is. What sort of throughput > > differences might it cause and under what circumstances? > > For the most part, this feature is motivated by internal parties who > have already established their opinions regarding swapping - the > workloads that are highly sensitive to IO, and especially those who > are using servers with really slow disk performance (for instance, > massive but slow HDDs). For these folks, it's impossible to convince > them to even entertain zswap if swapping also comes as a packaged > deal. Writeback disabling is quite a useful feature in these > situations - on a mixed workloads deployment, they can disable > writeback for the more IO-sensitive workloads, and enable writeback > for other background workloads. > > (Maybe we should include the paragraph above as part of the changelog?) I pasted it in, thanks.