On Thu, 28 Jul 2011, Christian Brunner wrote: > When I look at the latencytop results, there is a high latency when > calling "btrfs_commit_transaction_async". Isn't "async" supposed to > return immediately?
It depends. That function has to block until the commit has started before returning in the case where it creates a new btrfs root (i.e., snapshot creation). Otherwise a subsequent operation (after the ioctl returns) can sneak in before the snapshot is taken. (IIRC there was also another problem with keeping internal structures consistent, tho I'm forgetting the details.) And there are a bunch of things btrfs_commit_transaction() does before setting blocked = 1 that can be slow. There is a fair bit of transaction commit optimization work that should eventually be done here that we sadly haven't had the resources to look at yet. sage -- To unsubscribe from this list: send the line "unsubscribe ceph-devel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
