PGInfos are updated on disk with every write to the PG. I'm surprised
that one PG has so much more activity than the others, but that's why
that inode has so much activity.
What are you doing with this installation, and roughly how many PGs
are on the node?
On Thu, Nov 24, 2011 at 3:33 AM, Christian Brunner <chb@xxxxxx> wrote:
> I'm running a btrfs-debug patch on one of our nodes. This patch prints
> calls to btrfs_orphan_add. I'm still waiting for the problem the patch
> was intended to trace, but in the logs I found something ceph related
> I don't understand:
>
> When I look at the btrfs_orphan_add messages there is one inode that
> is updated over and over again. When I count the inodes in my log, I
> can see the following distribution (only inodes with more than 500
> btrfs_orphan_add calls listed):
>
> #cnt Inode
> 1117 7403
> 17218 7457
> 848 7484
> 539 7984
> 1446 9098
> 635 9346
>
> When I look at the filesysteme, I can see that inode 7457 belongs to:
>
> current/meta/DIR_8/DIR_A/pginfo\u2.8d__0_28D2BFA8
>
> I don't know how the pginfo stuff works, but I really wonder why the
> distribution is so uneven.
>
> "strace -f | grep 28D2BFA8" is giving me the this output:
>
> [...]
> [pid 3840] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=8, ...}) = 0
> [pid 3840] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=8, ...}) = 0
> [pid 3840] truncate("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> 0) = 0
> [pid 3840] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> [pid 3840] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> [pid 3840] open("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> O_WRONLY|O_CREAT, 0644) = 64
> [pid 3841] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=8, ...}) = 0
> [pid 3841] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=8, ...}) = 0
> [pid 3841] truncate("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> 0) = 0
> [pid 3841] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> [pid 3841] stat("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
> [pid 3841] open("/ceph/osd.015/current/meta/DIR_2/pginfo\\u2.d6__0_28D16932",
> O_WRONLY|O_CREAT, 0644) = 64
> [...]
>
> Regards,
> Christian
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