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b=hx7Duybr78IeEsr/EImsxu6uIAwwA+fZXVTBNX+bBzb8Q2ioN/qZ9CLLDLhVYy14b 206BpUY4e94wgEIV7RPj5R7hhMB5+kIvC/h7akfAYKg0lpbAR5yqTvAqlkKDbYyiwz +xq/GFmEmVU5K7t5GoxPq2YcHdlYz7gDfH19fAlM= Date: Fri, 14 Jun 2024 19:59:21 -0700 From: Andrew Morton To: Chris Li Cc: Kairui Song , Ryan Roberts , "Huang, Ying" , Kalesh Singh , linux-kernel@vger.kernel.org, linux-mm@kvack.org, Barry Song Subject: Re: [PATCH v2 0/2] mm: swap: mTHP swap allocator base on swap cluster order Message-Id: <20240614195921.a20f1766a78b27339a2a3128@linux-foundation.org> In-Reply-To: References: <20240614-swap-allocator-v2-0-2a513b4a7f2f@kernel.org> <20240614180606.5f3b6f4a6cd515df30b7a0e4@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: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 4BE654000B X-Stat-Signature: w9tf641hwxx57jntnxgm79wn6gpgbun8 X-HE-Tag: 1718420365-54418 X-HE-Meta: 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 YBuYsSlj mrRLBTLxE+i2IJC0yZNA7EZ5HSHe0uMbJH4/qE3nm0RG9BFNyGADkDGWveYl9USuEnYtByX8NWEk/PuxlolKKq3U3ke0d63uO0Mk+W8VTGguYxGYn0CnlU908vcLu+pyoISC00sG6o6ZdCxmsquWNQL4a7nVN37vcUZoiwAE5+oUx4/L/RhCb6EhGwocLqWGvU8wP0FsDycsuj2U/NPNJYS+Q9acjYL9GSNqgaAsK2a0mdFIIbwRekT9y+Q6ixin90oXqfScopri5jzYFyM5C8LLWKQ== 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 Fri, 14 Jun 2024 19:51:11 -0700 Chris Li wrote: > > I'm having trouble understanding the overall impact of this on users. > > We fail the mTHP swap allocation and fall back, but things continue to > > operate OK? > > Continue to operate OK in the sense that the mTHP will have to split > into 4K pages before the swap out, aka the fall back. The swap out and > swap in can continue to work as 4K pages, not as the mTHP. Due to the > fallback, the mTHP based zsmalloc compression with 64K buffer will not > happen. That is the effect of the fallback. But mTHP swap out and swap > in is relatively new, it is not really a regression. Sure, but it's pretty bad to merge a new feature only to have it ineffective after a few hours use. > > > > > There is some test number in the V1 thread of this series: > > > https://lore.kernel.org/r/20240524-swap-allocator-v1-0-47861b423b26@kernel.org > > > > Well, please let's get the latest numbers into the latest patchset. > > Along with a higher-level (and quantitative) description of the user impact. > > I will need Barray's help to collect the number. I don't have the > setup to reproduce his test result. > Maybe a follow up commit message amendment for the test number when I get it? Yep, I alter changelogs all the time. > > > > I'll add this into mm-unstable now for some exposure, but at this point > > I'm not able to determine whether it should go in as a hotfix for > > 6.10-rcX. > > Maybe not need to be a hotfix. Not all Barry's mTHP swap out and swap > in patch got merged yet. OK, well please let's give appropriate consideration to what we should add to 6.10-rcX in order to have this feature working well.