Date: Sat, 12 Aug 2017 11:50:34 -0400 From: Paul Kraus <paul@kraus-haus.org> To: "Eugene M. Zheganin" <emz@norma.perm.ru> Cc: freebsd-fs@freebsd.org, freebsd-stable <freebsd-stable@FreeBSD.org> Subject: Re: zfs listing and CPU Message-ID: <E3238E24-3AFA-4F2C-A299-D52E4D152097@kraus-haus.org> In-Reply-To: <aa26e888-05ef-c876-abf3-778ff08f4857@norma.perm.ru> References: <aa26e888-05ef-c876-abf3-778ff08f4857@norma.perm.ru>
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> On Aug 11, 2017, at 2:28 AM, Eugene M. Zheganin <emz@norma.perm.ru> = wrote: >=20 > Why does the zfs listing eat so much of the CPU ? > 47114 root 1 20 0 40432K 3840K db->db 4 0:05 26.84% = zfs > 47099 root 1 20 0 40432K 3840K zio->i 17 0:05 26.83% = zfs > 47106 root 1 20 0 40432K 3840K db->db 21 0:05 26.81% = zfs > 47150 root 1 20 0 40432K 3428K db->db 13 0:03 26.31% = zfs > 47141 root 1 20 0 40432K 3428K zio->i 28 0:03 26.31% = zfs > 47135 root 1 20 0 40432K 3312K g_wait 9 0:03 25.51% = zfs > This is from winter 2017 11-STABLE (r310734), one of the 'zfs'es is = cloning, and all the others are 'zfs list -t all'. I have like 25 gigs = of free RAM, do I have any chance of speeding this up using may be some = caching or some sysctl tuning ? We are using a simple ZFS web API that = may issue concurrent or sequential listing requests, so as you can see = they sometimes do stack. How many snapshots do you have ? I have only seen this behavior with = LOTS (not hundreds, but thousands) of snapshots. What does your `iostat -x 1` look like ? I expect that you are probably = saturating your drives with random I/O.
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