Re: rpc.mountd high cpu usage

[Karel Zak <kzak@redhat.com>]

On Mon, Jan 06, 2014 at 05:20:12PM +0100, Sander Klein wrote:
> Hi,
> 
> On 06.01.2014 12:18, Karel Zak wrote:
> >>> statfs("/some/export", {f_type=0x2fc12fc1, f_bsize=131072,
> >>> f_blocks=50331648, f_bfree=8355553, f_bavail=8355553,
> >>> f_files=2139121087, f_ffree=2139021753, f_fsid={1912623216,
> >>> 10933642}, f_namelen=255, f_frsize=131072}) = 0
> >>> stat("/some/export", {st_mode=S_IFDIR|0775, st_size=15, ...}) = 0
> >>> lstat("/some/export", {st_mode=S_IFDIR|0775, st_size=15, ...}) = 0
> >>> lstat("/some/export/..", {st_mode=S_IFDIR|0755, st_size=12288, ...}) = 0
> >>> stat("/some/export", {st_mode=S_IFDIR|0775, st_size=15, ...}) = 0
> >>> open("/sys/dev/block/0:187", O_RDONLY)  = -1 ENOENT (No such file or
> >>> directory)
> >
> >This is blkid_devno_to_devname(), the first attempt is /sys, but it
> >failed, then it tries to scan /dev (which is pretty expensive method).
> >
> >BTW, what is device 0:187?
> >
> >It seems like btrfs... maybe we can  optimize the code to ignore such
> >devices especially when get_uuid_blkdev() filters out btrfs :-)
> 
> This machine is running ZFS On Linux with 180 multipathed disks. I wouldn't
> be amazed if ZFS and BTRFS suffer from the same problem because they are
> both volume managers and filesystems in one.
> 
> >The another problem is poorly designed relationship between match_fsid()
> >and uuid_by_path().  The function uuid_by_path() is called in loop and
> >blkid is *always* requested, but the blkid_val is used when type==0.
> >It would be better to call get_uuid_blkdev() only when type==0.
> >
> >The patch below is just untested suggestion :-)
> 
> Should/Would ZFS_SUPER_MAGIC 0x2fc12fc1 be added to make this untested

yep, try it, test it ;-)

    Karel

-- 
 Karel Zak  <kzak@redhat.com>
 http://karelzak.blogspot.com