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Date:      Sat, 8 Dec 2018 22:09:43 +0300
From:      Lev Serebryakov <lev@FreeBSD.org>
To:        Mateusz Guzik <mjguzik@gmail.com>
Cc:        freebsd-hackers@freebsd.org, freebsd-current@freebsd.org
Subject:   ZFS sends TIRMs to agressively? (Was: Painfully slow compilation (read: "make buildworld buildkernel") on not-so-weak system)
Message-ID:  <1102394497.20181208220943@serebryakov.spb.ru>
In-Reply-To: <1844304999.20181208195837@serebryakov.spb.ru>
References:  <902729965.20181208141303@serebryakov.spb.ru>   <1034207210.20181208172042@serebryakov.spb.ru> <CAGudoHFz3e3g2VYq0UMnaoh45UULBh0ch0P_1FHmGuF%2B0U7nhQ@mail.gmail.com> <1844304999.20181208195837@serebryakov.spb.ru>

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Hello Lev,

Saturday, December 8, 2018, 7:58:37 PM, you wrote:

>> Can you please narrow the problem down to a specific kernel revision?
>  I'm still not sure it is software or hardware problem.
 Looks like Samsung 850 EVO doesn't like TRIMs sent by ZFS (and I've thought
it is good SSD, consumer-grade, but really good one!).

 I've tuned down TRIMs with

vfs.zfs.per_txg_dirty_frees_percent=10
vfs.zfs.free_max_blocks=1000
vfs.zfs.vdev.trim_max_active=4

And it MOSTLY solved problem: there are some freezing from time to time (and
strange consumption of CPU by low-profile threads) with these settings.

 When I've disabled TRIM completely all freezes are gone, and low-profile
threads consume tenths of percent of CPU, as it is intended.

-- 
Best regards,
 Lev                            mailto:lev@FreeBSD.org




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