kern/181226: Writes to almost full FS eat 100% CPU and speed drops below 1MB/sec
Dmitry Sivachenko
trtrmitya at gmail.com
Sun Aug 11 12:30:02 UTC 2013
>Number: 181226
>Category: kern
>Synopsis: Writes to almost full FS eat 100% CPU and speed drops below 1MB/sec
>Confidential: no
>Severity: serious
>Priority: low
>Responsible: freebsd-bugs
>State: open
>Quarter:
>Keywords:
>Date-Required:
>Class: sw-bug
>Submitter-Id: current-users
>Arrival-Date: Sun Aug 11 12:30:01 UTC 2013
>Closed-Date:
>Last-Modified:
>Originator: Dmitry Sivachenko
>Release: FreeBSD 9.2-BETA2 amd64
>Organization:
>Environment:
System: FreeBSD agata.yandex.ru 9.2-BETA2 FreeBSD 9.2-BETA2 #2 r253884M: Sun Aug 11 12:12:37 MSK 2013 mitya at agata.yandex.ru:/usr/obj/opt/WRK/src/sys/CAVIA amd64
FreeBSD-9.2-BETA2
>Description:
I have 25TB Dell PERC 6 RAID5 array. When it becomes almost full
(10-20GB free), processes which write data to it start eating 100% CPU and
write speed drops below 1MB/sec (normally to gives 400MB/sec).
1889 mitya 1 100 0 2058M 1027M CPU12 12 0:47 92.77% dd
systat -vm shows disk array is not busy:
Disks mfid0
KB/t 63.71
tps 65
MB/s 0.77
%busy 3
If I delete some files to free space during that slow write, the same process
starts writing with normal speed.
I was running that machine with ~1 year old 9-STABLE without any problems.
That array often overflows, and I always got "filesystem is full" error
without write speed reduction.
The probles appeared after I upgraded to 9.2-BETA2 few days ago.
tunefs: POSIX.1e ACLs: (-a) disabled
tunefs: NFSv4 ACLs: (-N) disabled
tunefs: MAC multilabel: (-l) disabled
tunefs: soft updates: (-n) enabled
tunefs: soft update journaling: (-j) disabled
tunefs: gjournal: (-J) disabled
tunefs: trim: (-t) disabled
tunefs: maximum blocks per file in a cylinder group: (-e) 4096
tunefs: average file size: (-f) 16384
tunefs: average number of files in a directory: (-s) 64
tunefs: minimum percentage of free space: (-m) 1%
tunefs: space to hold for metadata blocks: (-k) 0
tunefs: optimization preference: (-o) space
tunefs: volume label: (-L)
>How-To-Repeat:
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
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