Date: Sun, 13 Aug 2017 15:09:23 +0500 From: "Eugene M. Zheganin" <emz@norma.perm.ru> To: freebsd-fs@freebsd.org Cc: freebsd-stable <freebsd-stable@FreeBSD.org> Subject: Re: zfs listing and CPU Message-ID: <399c4309-c7a6-a7e9-299f-9675224c090d@norma.perm.ru> In-Reply-To: <E3238E24-3AFA-4F2C-A299-D52E4D152097@kraus-haus.org> References: <aa26e888-05ef-c876-abf3-778ff08f4857@norma.perm.ru> <E3238E24-3AFA-4F2C-A299-D52E4D152097@kraus-haus.org>
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Hi,
On 12.08.2017 20:50, Paul Kraus wrote:
>> On Aug 11, 2017, at 2:28 AM, Eugene M. Zheganin <emz@norma.perm.ru> wrote:
>>
>> 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.
[root@san1:~]# zfs list -t snapshot | wc -l
88
> What does your `iostat -x 1` look like ? I expect that you are probably saturating your drives with random I/O.
Well, it's really long, and the disks are busy with random i/o indeed,
but byst only for 20-30%. As about iostat - it's really long, because I
have hundreds (not thousands) of zvols, and they do show up in iostat
-x. But nothing unusual besides that.
Thanks.
Eugene.
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