Linux: Report reclaimable memory to kernel as such #16385
Conversation
Linux provides SLAB_RECLAIM_ACCOUNT and __GFP_RECLAIMABLE flags to mark memory allocations that can be freed via shinker calls. It should allow kernel to tune and group such allocations for lower memory fragmentation and better reclamation under pressure. This patch marks as reclaimable most of ARC memory, directly evictable via ZFS shrinker, plus also dnode/znode/sa memory, indirectly evictable via kernel's superblock shrinker. Signed-off-by: Alexander Motin <[email protected]> Sponsored by: iXsystems, Inc.
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Could we get one more reviewer on this one? |
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While I think the changes (and goals!) make sense, I don't appear to be able to see a difference in either the kernel's accounting of free/available memory (casually tested via 'free' and similar) or general eviction behavior. Tested (as I said, casually - filling ARC, applying slow or fast memory pressure, applying non-ARC pagecache pressure, etc, eyeing 'free' and other end-user memory stat gatherers) with a Linux 6.8 kernel. Is there a specific stat or testing pattern where this is clearly functional and beneficial? Thanks. |
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@adamdmoss SLAB_RECLAIM_ACCOUNT memory should be included into SReclaimable in /proc/meminfo and then into available memory, which as I see should be used by different balloon drivers. __GFP_RECLAIMABLE I haven't found to be reported directly, but I understand it to be grouped together as Reclaimable migration type, as reported in /proc/pagetypeinfo. |
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Thanks, that makes some sense. |
Linux provides SLAB_RECLAIM_ACCOUNT and __GFP_RECLAIMABLE flags to mark memory allocations that can be freed via shinker calls. It should allow kernel to tune and group such allocations for lower memory fragmentation and better reclamation under pressure. This patch marks as reclaimable most of ARC memory, directly evictable via ZFS shrinker, plus also dnode/znode/sa memory, indirectly evictable via kernel's superblock shrinker. Signed-off-by: Alexander Motin <[email protected]> Sponsored by: iXsystems, Inc. Reviewed-by: Tony Hutter <[email protected]> Reviewed-by: Allan Jude <[email protected]>
…6385)" This reverts commit d4b5517. Signed-off-by: Pavel Snajdr <[email protected]>
Linux provides SLAB_RECLAIM_ACCOUNT and __GFP_RECLAIMABLE flags to mark memory allocations that can be freed via shinker calls. It should allow kernel to tune and group such allocations for lower memory fragmentation and better reclamation under pressure.
This patch marks as reclaimable most of ARC memory, directly evictable via ZFS shrinker, plus also dnode/znode/sa memory, indirectly evictable via kernel's superblock shrinker.
Types of changes
Checklist:
Signed-off-by.