zfs, mc, mcview and files opening

[Eugene Grosbein]

On 10.11.2015 18:56, Marko Turk wrote:
> Hi,
> 
> On Tue, Nov 10, 2015 at 02:58:32PM +0500, Eugene M. Zheganin wrote:
>> Hi.
>>
>> my midnight commander is terribly slow at vieweing files with mcview.
>> Opening of a file of approximately 10 megabytes takes about 30-40
>> seconds. This isn't related with the compression setting, %busy wait or
>> pool properties- I tested on various machines, it's fully reproducible.
>> This lag appears on files about 1.5 megs in size, and the lag time is
>> pretty constant.  From my observation, it's the following syscall that's
>> blocking:
>>
>> fstat(4,{ mode=p--------- ,inode=41,size=0,blksize=4096 }) = 0 (0x0)
>> (observed using `truss mcview maillog`)
>>
>> If the file is viewed not by mcview (i.e. it is of a special type and
>> viewed by the special utility, or mcview is simply not used - for
>> example more opens same file without lag) - the file is opening fast as
>> always. When mcview is involved - lag appears. In the same time I've
>> never seen this lag on filesystems other than zfs.
> 
> Is this happening on every ZFS FreeBSD install or just some of them? I'm
> running ZFS on FreeBSD 10-STABLE and I don't see this problem (even for
> much larger files).

The problem has already been fixed with import of file-5.25 and MFC to stable/10:
https://svnweb.freebsd.org/base?view=revision&revision=290152