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

Warner Losh imp at bsdimp.com
Wed May 25 17:50:13 UTC 2011


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

From: Warner Losh <imp at bsdimp.com>
To: Alex Bakhtin <alex.bakhtin at gmail.com>
Cc: bug-followup at FreeBSD.org, imp at FreeBSD.org
Subject: Re: misc/145395: [nanobsd] [patch] Extremely slow nanobsd disk image creation and 100% disk load on zfs
Date: Wed, 25 May 2011 11:38:46 -0600

 If you are doing soft updates, you can't do async.  They are mutually =
 exclusive.  Soft updates usually are a big win for creation, but might =
 need to be turned off for async operations.
 
 If you have an updated patch against -current, please let me know.
 
 Warner
 
 On May 25, 2011, at 7:35 AM, Alex Bakhtin wrote:
 
 > Hello,
 >=20
 >=20
 >> 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.
 >=20
 >   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.
 >=20
 > /dev/md2s1a on /mnt/system/obj/amtkit/_.mnt (ufs, local, soft-updates)
 >=20
 >   I tried to mout in async manually - and it seems that async option
 > is ignored for MD-backed filesystem:
 >=20
 > bakhtin at tarzan(14) /mnt/system/nanobsd/amtkit
 >> sudo umount /mnt/system/obj/amtkit/_.mnt
 >=20
 > bakhtin at tarzan(14) /mnt/system/nanobsd/amtkit
 >> sudo mount -o async /dev/md2s1a //mnt/system/obj/amtkit/_.mnt
 >=20
 >> 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)
 >=20
 > As you can see - md2s1a is not mounted in async mode, and this causes
 > extremely bad performance on ZFS.
 >=20
 > I'm pretty sure that attaching MD in async mode fixes this problem.
 > Please review my patch and this bug.
 >=20
 >=20
 > --
 > ---
 > Alex Bakhtin
 >=20
 >=20
 


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