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Fri, 09 Jan 2026 16:32:13 +0800 Message-ID: Date: Fri, 9 Jan 2026 16:32:12 +0800 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH] arm64: Kconfig: enable ARCH_WANTS_THP_SWAP for all pagesizes To: Barry Song <21cnbao@gmail.com>, Will Deacon Cc: Catalin Marinas , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Andrew Morton , David Hildenbrand , linux-mm@kvack.org, baolin.wang@linux.alibaba.com References: <20251226063759.4020782-2-tongweilin@linux.alibaba.com> Content-Language: en-US From: Weilin Tong In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit X-Stat-Signature: 71he6j9bjyyjs1bzcqe89wfmwn3e8poe X-Rspamd-Queue-Id: 4165D40007 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1767947537-418080 X-HE-Meta: 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 tIVXWgPD jaD+D4j4+3IgzxplyE8wTS1f9SWj7pqDUfLocJnWAc3Oo6HigEQM7DBCxFh9TDB8EWtG6qQm2oCLthJxaXsgZRdPz5Lc4xblqYO5j5HxSggZFVBgavV59MFxE2d0eOPeQ3li5tGANM5+WeJ64MN0NqM8eq+Lkzz31GMTg0wWMGcrvKurIloqatfc5vL6oASprMghfna6LGNlSxSAcFAqt12vXu2OkutMoRH93kiC3tTNnQHWZvJmuzvtRHyOuroKJMpcbuvgVvQyuya+d1zvWRS47xNfq6aeFvL7jLyau7bfo5jC9H0oPUJ5pJDz+TOVuNNwjsZpjkbBEnbZ5t/Df6/ZZwYHR5NqgD/VNxFKWi62SYhFVUwvbI1bgo9RY7+S37ToBvTYv3puKJMx0hO3ncoJRybdpPHn0OPDO 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: 在 2026/1/9 07:11, Barry Song 写道: > On Fri, Jan 9, 2026 at 7:29 AM Will Deacon wrote: >> On Fri, Dec 26, 2025 at 07:52:44PM +1300, Barry Song wrote: >>> On Fri, Dec 26, 2025 at 7:39 PM Weilin Tong >>> wrote: >>>> Currently, ARCH_WANTS_THP_SWAP was limited to 4K page size ARM64 kernels, but >>>> large folios requiring swapping also exist in other page size configurations >>>> (e.g. 64K). Without this config, large folios in these kernels cannot be swapped >>>> out. >>>> >>>> Here we enable ARCH_WANTS_THP_SWAP for all ARM64 page sizes. >>> I no longer recall why this was not enabled for sizes other than >>> 4 KB in commit d0637c505f8a ("arm64: enable THP_SWAP for arm64"), but >>> it appears to be fine, and the swap cluster size should also be >>> more friendly to PMD alignment. >> You seemed to be worried about I/O latency in your original post: >> >> https://lore.kernel.org/all/20220524071403.128644-1-21cnbao@gmail.com/ > Will, thanks for pointing this out! With a 16KB page size, a PMD > covers 32MB; with 64KB pages, a PMD covers 512MB. So, Weilin, are > we ready to wait for 32MB or 512MB to be written out before > memory can be reclaimed? By splitting, we can reclaim memory > earlier while only part of it has been swapped out. I got your point. In our production envs using 64K pagesize kernel, we only enable 2M and below size mthp, so swapping out as a whole is a better way. Or maybe we can set the SWAPFILE_CLUSTER by arch. I will do some tests of this concern. Thanks a lot. > While splitting down to order-0 is not ideal, splitting to a > relatively larger order appears to strike a balance between I/O > latency and swap performance. Anyway, I don't know :-) > > Thanks > Barry