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Date:      Mon, 18 Mar 2019 13:07:49 +0000
From:      Pete French <petefrench@ingresso.co.uk>
To:        freebsd-stable@freebsd.org
Subject:   Re: Observations from a ZFS reorganization on 12-STABLE
Message-ID:  <2baf16fd-3767-1dda-d519-995f7ebaf0cb@ingresso.co.uk>
In-Reply-To: <e5c648b4-ba73-5d3a-2924-be4d52e4c267@grosbein.net>
References:  <58eb1994-41bd-cd22-be66-0024bcbc36e6@denninger.net> <e5c648b4-ba73-5d3a-2924-be4d52e4c267@grosbein.net>

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On 17/03/2019 21:57, Eugene Grosbein wrote:
> I agree. Recently I've found kind-of-workaround for this problem:
> increase vm.v_free_min so when "FREE" memory goes low,
> page daemon wakes earlier and shrinks UMA (and ZFS ARC too) moving some 
> memory
> from WIRED to FREE quick enough so it can be re-used before bad things 
> happen.
> 
> But avoid increasing vm.v_free_min too much (e.g. over 1/4 of total RAM)
> because kernel may start behaving strange. For 16Gb system it should be 
> enough
> to raise vm.v_free_min upto 262144 (1GB) or 131072 (512M).
> 
> This is not permanent solution in any way but it really helps.

Ah, thats very interesting, thankyou for that! I;ve been bitten by this 
issue too in the past, and it is (as mentioned) much improved on 12, but 
the act it could still cause issues worries me.

-pete.



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