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Date:      Mon, 15 Jul 2024 13:23:35 +0200
From:      Peter <pmc@citylink.dinoex.sub.org>
To:        freebsd-fs@freebsd.org
Subject:   Can ZFS ARC be run with roundrobin policy?
Message-ID:  <ZpUGt8f6zvZ4Codz@disp.intra.daemon.contact>

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Hi,
  from what I perceive, the ZFS ARC allocates in firsttouch
policy, like so:

# cpuset -gp $$
pid 56305 mask: 6, 7, 8, 9
pid 56305 domain policy: prefer mask: 2
# cpuset -gd 0
domain 0 mask: 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
$ sysctl vm.domain | grep free_c
vm.domain.3.stats.free_count: 2994244
vm.domain.2.stats.free_count: 3030568
vm.domain.1.stats.free_count: 2913977
vm.domain.0.stats.free_count: 5368353        <<

# find /media/sysimg -type f | xargs cat > /dev/null
$ sysctl vm.domain | grep free_c
vm.domain.3.stats.free_count: 2994297
vm.domain.2.stats.free_count: 3030217
vm.domain.1.stats.free_count: 2937179
vm.domain.0.stats.free_count: 884588         <<


This is not always to my liking. I would prefer roundrobin
allocations here. But, I didn't easily find a switch, and, reading
into the UMA allocator, it states that it can do roundrobin, but it is
not so easily figured how that be made happen in practice.

Pointers on where I might look into, are welcome.

regards,
PMc



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