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Mon, 06 Jan 2025 02:19:53 -0800 (PST) MIME-Version: 1.0 References: <9404aaa2-4fc2-4b8b-8f95-5604c54c162a@redhat.com> <3f3c7254-7171-4987-bb1b-24c323e22a0f@redhat.com> <0ed5241e-10af-43ee-baaf-87a5b4dc9694@redhat.com> <446704ab-434e-45ac-a062-45fef78815e4@redhat.com> In-Reply-To: From: Miklos Szeredi Date: Mon, 6 Jan 2025 11:19:42 +0100 Message-ID: Subject: Re: [PATCH v6 4/5] mm/migrate: skip migrating folios under writeback with AS_WRITEBACK_INDETERMINATE mappings To: David Hildenbrand Cc: Joanne Koong , Shakeel Butt , Bernd Schubert , Zi Yan , linux-fsdevel@vger.kernel.org, jefflexu@linux.alibaba.com, josef@toxicpanda.com, linux-mm@kvack.org, kernel-team@meta.com, Matthew Wilcox , Oscar Salvador , Michal Hocko Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: CAC861A0013 X-Stat-Signature: 31owbru96an15uso9ngmjtzpxgiorso7 X-Rspam-User: X-HE-Tag: 1736158794-468187 X-HE-Meta: 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 oewHwhqM EUZtPLo2UHfF7Pl0ZJeFPIvKSzukNOFqhGEriRUse7z1xx7CbziWjZzDtl+/wBLEOvjDHHYkprORwc0YYBYIOk0133DZqRUcmYDWuo1q0TpM0EffysTpb6YpK+YsxMy139Cbw5JidrvcjYb2KCvod4egRjIIJ35OOmgTEZrpquvBhsuQ1X0sg13G/mitg7BdXhjH+aO6T1vjQIz/BWAofLYPrMSajcaqApWZv0I/SSCTJKxNUYSUZi+WtzdKFR1uDAXhszsa2x0+WA2gQzPloTo47/awBl6kk+PTz X-Bogosity: Ham, tests=bogofilter, spamicity=0.000254, 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, 3 Jan 2025 at 21:31, David Hildenbrand wrote: > In any case, having movable pages be turned unmovable due to persistent > writaback is something that must be fixed, not worked around. Likely a > good topic for LSF/MM. Yes, this seems a good cross fs-mm topic. So the issue discussed here is that movable pages used for fuse page-cache cause a problems when memory needs to be compacted. The problem is either that - the page is skipped, leaving the physical memory block unmovable - the compaction is blocked for an unbounded time While the new AS_WRITEBACK_INDETERMINATE could potentially make things worse, the same thing happens on readahead, since the new page can be locked for an indeterminate amount of time, which can also block compaction, right? What about explicitly opting fuse cache pages out of compaction by allocating them form ZONE_UNMOVABLE? Thanks, Miklos