Messages in this thread | | | From | Ilya Dryomov <> | Date | Wed, 29 Mar 2017 13:10:01 +0200 | Subject | Re: [PATCH 4.4 48/76] libceph: force GFP_NOIO for socket allocations |
| |
On Wed, Mar 29, 2017 at 12:55 PM, Michal Hocko <mhocko@kernel.org> wrote: > On Wed 29-03-17 12:41:26, Michal Hocko wrote: > [...] >> > ceph_con_workfn >> > mutex_lock(&con->mutex) # ceph_connection::mutex >> > try_write >> > ceph_tcp_connect >> > sock_create_kern >> > GFP_KERNEL allocation >> > allocator recurses into XFS, more I/O is issued > > One more note. So what happens if this is a GFP_NOIO request which > cannot make any progress? Your IO thread is blocked on con->mutex > as you write below but the above thread cannot proceed as well. So I am > _really_ not sure this acutally helps.
This is not the only I/O worker. A ceph cluster typically consists of at least a few OSDs and can be as large as thousands of OSDs. This is the reason we are calling sock_create_kern() on the writeback path in the first place: pre-opening thousands of sockets isn't feasible.
Thanks,
Ilya
| |