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Thu, 05 Nov 2026 03:43:02 -0800 (PST) Message-ID: Date: Thu, 5 Nov 2026 12:43:00 +0100 X-Archived-By: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, vmscan: make kswapd unreserve highatomic pageblocks To: "Vlastimil Babka (SUSE)" , Johannes Weiner Cc: Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Zi Yan , David Hildenbrand , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , JP Kobryn , Frank van der Linden , Thadeu Lima de Souza Cascardo , Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20261104-kswapd-highatomic-unreserve-v1-1-38be5106adf5@kernel.org> <75540cfc-0577-4d91-9369-d1c4fe9c3096@gmail.com> <76431b4e-27b4-4922-bc59-bf97516b40fc@kernel.org> Content-Language: en-US From: "Jose A. Perez de Azpillaga" In-Reply-To: <76431b4e-27b4-4922-bc59-bf97516b40fc@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Stat-Signature: zesutxe7qoyd771w6zmdo73tgfpu7ogf X-Rspamd-Server: rspam01 X-Rspam-User: X-Spam-Status: No, score=-4.3 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_PASS, SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=4.0.1 X-Rspamd-Queue-Id: A7609120004 X-HE-Tag: 1793878984-41707 X-HE-Meta: U2FsdGVkX1+qUI1OsX06fT/QjsO20acqQ46mgtKYs25m/oyXMTQ+eMXtKw/9WbNBdfiV4FtHPWEZBBNgOu8UY3hFvlir6RBkjBB/F54h7pDfTjDe9+k1JaZrme4GlhEJoBsVz54E+XvAbZwdjLi/cEsXI4/cDyEL++4SX+04oJYVEZ+Ki3xhX73wujE9GjxrIIvTrIWZaN8/ew17wBXDAA6Ovyuc5V2WBvwUuysVKDH7oFtJsG+4IjkVj/yPTZ/Fxj9g1OkCs9FKfGewrrdrljPBxwwW8+jn+b+z2W/QC3uD+PM8EeiACbFsYTJVHDOg6p6a9/+e1IsFV0O2poTZS5WOlZYzSWebKuCzhu3EIxg+1G2K1qCuLm8agx5MyaZtEOukct162dbkE/QrIuEd63VoT+7s/wyRwOfzsjPhKHtDKgB3nNnzhVJF3qOrvIzFQbQ5ZUFFdiaDupZL9Kctl/VXYjiHVhTUzsEpOtoqNfVqRPApV6/tz5YU8ZAZbxy79QABWaHuEQ/Cwb9NaBQlQwaO98O9bOkWhbDX8TFlPlUtPu/bz0xxnjGQMBO8Hvb5wapFPlXv11mQFCBEDJIHZemuwnSmMwIDdvaKZUIusMKugFvegFHI0QqVQgp2ourBshe9LkigSmEPkCOqlDv9ThGkdc/LtcTvs5lghNPQAz1rFANB/QYg6odhXLebmZNGJtgwnwUb5iCX/JxFf8glzG6b6Ub9Bv/BKtq+Db9ymoG5sk5PTbHfbK167H1OIVO7pIpAIo1dQfYThqyrTTZOCBoq35rjpJnrcGqSbWRTCPvuT5UcvpSx5pkljYfwqoyXIngozYusFOFQIPYAEFmw6SI6vbqReE/7+dHwVhZCcg0TOALH68xGZ9z6PdfpnfOnomBqVQLVrKVLj3NyKhpuWNjOCYWCmESYWfDCle8RitRYg9wx+A5WwuO6Qtm3QanilnD7tSYn4AzkK/0cqYK JVhYvR+h R6RSl58XndXMW4uzWbyXWg0P/aQ2/mFkbZGLkbIv8waV0fj8KNirY1w0RaabtPp4vMhi8+qbLvAt8PbWn9VISp2S6jVCGbMVTl7dxHvYwd2mhGVJiEZdzQZkX5j0uQWhd7GwDROsbL6HDz9qxCAabYIhYYx431ZQDJHjua9TGI5cO2Moii1xy1Nio+wJPKcQKW8Ab2Rya/bUKZV+/T/VpYx6YNXRmKFCwQ1GXXTQpb0uiM8fXPOdYYSrNjEhycz+VGNo1FvzgLyUYxwjP27vMknHlW9k/r4qmssM7pmp94O/PjLOrcFP95W2fbIkW6eItAejDRqifGZdSmkm/RhSz10WHvRStBG3uTGzC7yo/jejZRrgkI4pp8U5kHxK6Vqm9xfcClPaa9YcphVFFfctD9/x4flh7aNcCzy1liVgp1Y3J5ahE5o06bts6Ua5CPp2wYE6P Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On 11/5/26 9:02 AM, Vlastimil Babka (SUSE) wrote: > On 11/4/26 22:56, Jose A. Perez de Azpillaga wrote: >> On 11/4/26 7:38 PM, Vlastimil Babka (SUSE) wrote: >>> Hook this highatomic unreserve to the moment we are increasing kswapd >>> reclaim priority, as that is when kswapd is struggling to make progress >>> and it should roughly match the case of direct reclaim failure. >>> >> >> isn't raise_priority true after almost every pass at DEF_PRIORITY, stuck >> or not? > > Can you elaborate why? At least at first glance, kswapd_shrink_node() should > return true if it scans the requested amount of pages. So I would assume > that although balance_pgdat() will do multiple iterations to reach high > watermarks (because every round of kswapd_shrink_node() will limit itself to > SWAP_CLUSTER_MAX per zone for sc->nr_to_reclaim) this should not be raising > priority if the rounds are successful? > it's max(high_wmark_pages(zone), SWAP_CLUSTER_MAX) per zone, so the sum of the high watermarks. by default that's at least managed/500, while DEF_PRIORITY scans lru >> 12, so it can't return true above priority 8 even when every round is successful. and sc.priority-- runs before pgdat_balanced() is rechecked, so a wakeup that balances the node in one pass still unreserves a pageblock per zone. -- cheers, jose a. p-a