misc/145395: [nanobsd] [patch] Extremely slow nanobsd disk image creation and 100% disk load on zfs

[Alex Bakhtin]

The following reply was made to PR misc/145395; it has been noted by GNATS.

From: Alex Bakhtin <alex.bakhtin at gmail.com>
To: bug-followup at freebsd.org, imp at freebsd.org
Cc:  
Subject: Re: misc/145395: [nanobsd] [patch] Extremely slow nanobsd disk image
 creation and 100% disk load on zfs
Date: Wed, 25 May 2011 17:35:50 +0400

 Hello,
 
 
 >From-To:open->closed
 >By:imp When:Fri May 13 13:44:33 MDT 2011
 >Why:We've been doing async for a while now. Bug OBE.
 
    I'm really sorry, but today I have tested the nanobsd.sh from
 9-CURRENT and I'm completely sure that the problem WAS NOT fixed. I
 discovered that building image is still extremelly slow and produces
 great disk load. After checking deeply, I found that image is not
 mounted in async mode.
 
 /dev/md2s1a on /mnt/system/obj/amtkit/_.mnt (ufs, local, soft-updates)
 
    I tried to mout in async manually - and it seems that async option
 is ignored for MD-backed filesystem:
 
 bakhtin at tarzan(14) /mnt/system/nanobsd/amtkit
 > sudo umount /mnt/system/obj/amtkit/_.mnt
 
 bakhtin at tarzan(14) /mnt/system/nanobsd/amtkit
 > sudo mount -o async /dev/md2s1a //mnt/system/obj/amtkit/_.mnt
 
 > mount | grep md
 /dev/md0 on /etc (ufs, local)
 /dev/md1 on /var (ufs, local)
 /dev/md2s1a on /mnt/system/obj/amtkit/_.mnt (ufs, local, soft-updates)
 
 As you can see - md2s1a is not mounted in async mode, and this causes
 extremely bad performance on ZFS.
 
 I'm pretty sure that attaching MD in async mode fixes this problem.
 Please review my patch and this bug.
 
 
 --
 ---
 Alex Bakhtin