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AJvYcCUo0eqYtkYl6bzdvsot1H4YbmUOOOGdvwfVzOs/WZpibOHqPksHcAHm3VbNGIlHy30pTf65sFi+1Q==@kvack.org X-Gm-Message-State: AOJu0YyPVb6mQVZQQMPMTeYf+rlh/XjqSwV8SuygovWwgFPNvU/ZD8RL UglOSJBY9iqDM8UT97I50isNthdkbplyR7fYpBKu8EI9bt6gFfswPKGzqEjoS0xCR4pwhq3nT/E Mbw4wEUrmnGb2SRX2OlaEtOP2yXKPwKZrAXw= X-Gm-Gg: ASbGncuU6eJCR3ruSvJvRd2gPyRWG+D3pLdLvx38iDNm9ViI/fzsr/eDQ/naWsz2UqO lntGGoV/Z6SbhwFKoDIYuIMNyHyJXahpksJ9tuFw= X-Google-Smtp-Source: AGHT+IG+63EtOhDnrCHSjhF6lazy8k8xjOrpZg0xQsQYkT32Inl5S5jcsXMUS6WBs+UHNx64ATrDpXdmxdRBN/uBffw= X-Received: by 2002:a05:6214:449f:b0:6d8:a4fd:d253 with SMTP id 6a1803df08f44-6df9b22d70emr56150356d6.21.1736351408935; Wed, 08 Jan 2025 07:50:08 -0800 (PST) MIME-Version: 1.0 References: <20250107222236.2715883-1-yosryahmed@google.com> <20250107222236.2715883-2-yosryahmed@google.com> <857acdc4-c4b7-44ea-a67d-2df83ca245ed@linux.dev> In-Reply-To: From: Nhat Pham Date: Wed, 8 Jan 2025 22:49:57 +0700 X-Gm-Features: AbW1kvbu9OvcJKSIkNlMys8ykTcz32E6i4Oop0mw4VMYPzfy2vU9G3foGtSsz9U Message-ID: Subject: Re: [PATCH v2 2/2] mm: zswap: disable migration while using per-CPU acomp_ctx To: Yosry Ahmed Cc: Barry Song <21cnbao@gmail.com>, Chengming Zhou , Johannes Weiner , Andrew Morton , Vitaly Wool , Sam Sun , "linux-mm@kvack.org" , "linux-kernel@vger.kernel.org" , "stable@vger.kernel.org" , "Sridhar, Kanchana P" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: kw4jxka53kknhqocwmdiigwmzoddirbk X-Rspamd-Queue-Id: 22E841C0018 X-Rspam-User: X-Rspamd-Server: rspam01 X-HE-Tag: 1736351409-28655 X-HE-Meta: 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 KSUyY7d1 M/A+KJn7v4Z2DgayTYPKEUiSkSVHiNhYaDT3fRCMyg602daY29c9GaTmtubi4WzIiytjC1D81AmPbgnPDhdIr9m9rNGu4R9CLvzFKuahWd9WohLN1Tm71ejX38XWRfiip4tvUhcG/3xWkFJYkCRWleiszYTTkzBQlaEf+fH6gSeFBrgO13UQdkZsJZm4uCg8vaO5fqMnIuM84PDWiXtyQ4/DIrN/DyhJV111iC7QsEH6BmazhGnFnB9U3lJ8T6D0fGVXtHL4aO6qCyLqSSzU5/6o6H6+ixGUSMnxj0C+aAwM+FUaLIHkvRJhn57cj9R39uPy/OkNpJySAXNWD39N74fKeL1uxl/qob9RqDIZ3B3oiyl8O3F4Mmu9yommorzu+OWc6UGDCmX1zrNw= X-Bogosity: Ham, tests=bogofilter, spamicity=0.028578, 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 Wed, Jan 8, 2025 at 10:36=E2=80=AFPM Yosry Ahmed = wrote: > > > Oh, I was not talking about my proposed diff, but the existing logic > that allocates the requests and buffers in the hotplug callbacks > instead of just using alloc_percpu() to allocate them once for each > possible CPU. I was wondering if there are actual setups where this > matters and a significant amount of memory is being saved. Otherwise > we should simplify things and just rip out the hotplug callbacks. My vote is for ripping the hotplug callbacks (eventually) :) In addition to the discrepancy in the number of possible and online CPUs, we also need a relatively smaller memory size for the discrepancy to matter, no? Systems with hundreds of CPUs (hopefully) should have hundreds of GBs worth of memory available (if not more). Anyhow, we can just go with the diff you sent for now (and for past kernels). Seems simple enough, and wouldn't get in the way of the eventual hotplug logic removal (if you decide to pursue it).