Rik van Riel 1aa43598c0 mm: remove unnecessary calls to lru_add_drain ...

There seem to be several categories of calls to lru_add_drain and
lru_add_drain_all.

The first are code paths that recently allocated, swapped in, or otherwise
processed a batch of pages, and want them all on the LRU.  These drain
pages that were recently allocated, probably on the local CPU.

A second category are code paths that are actively trying to reclaim,
migrate, or offline memory.  These often use lru_add_drain_all, to drain
the caches on all CPUs.

However, there also seem to be some other callers where we aren't really
doing either.  They are calling lru_add_drain(), despite operating on
pages that may have been allocated long ago, and quite possibly on
different CPUs.

Those calls are not likely to be effective at anything but creating lock
contention on the LRU locks.

Remove the lru_add_drain calls in the latter category.

For detailed reasoning, see [1] and [2].

Link: https://lkml.kernel.org/r/dca2824e8e88e826c6b260a831d79089b5b9c79d.camel@surriel.com [1]
Link: https://lkml.kernel.org/r/xxfhcjaq2xxcl5adastz5omkytenq7izo2e5f4q7e3ns4z6lko@odigjjc7hqrg [2]
Link: https://lkml.kernel.org/r/20241219153253.3da9e8aa@fangorn
Signed-off-by: Rik van Riel <riel@surriel.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: David Hildenbrand <david@redhat.com>
Acked-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com>
Cc: Chris Li <chrisl@kernel.org>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

2025-01-25 20:22:21 -08:00

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