** Description changed:
+ == SRU Justification ==
+
+ [Impact]
+ Occasionally an application gets stuck in "D" state on NFS reads/sync and
close system calls. All the subsequent operations on the NFS mounts are stuck
and reboot is required to rectify the situation.
+
+ [Fix]
+ Use GPF_NOIO in some allocations in writeback to avoid a deadlock. This is
upstream in:
+ ae97aa524ef4 ("NFS: Use GFP_NOIO for two allocations in writeback")
+
+ [Testcase]
+ See Test scenario in previous description.
+
+ A test kernel with this patch was tested heavily (>100hrs of test suite)
+ without issue.
+
+ [Regression Potential]
+ This changes memory allocation in NFS to use a different policy. This could
potentially affect NFS.
+
+ However, the patch is already in Artful and Bionic without issue.
+
+ The patch does not apply to Trusty.
+
+ == Previous Description ==
+
Using Ubuntu Xenial user reports processes hang in D state waiting for
disk io.
Ocassionally one of the applications gets into "D" state on NFS
reads/sync and close system calls. based on the kernel backtraces seems
to be stuck in kmalloc allocation during cleanup of dirty NFS pages.
All the subsequent operations on the NFS mounts are stuck and reboot is
required to rectify the situation.
[Test scenario]
- 1) Applications running in Docker environment
- 2) Application have cgroup limits --cpu-shares --memory -shm-limit
- 3) python and C++ based applications (torch and caffe)
- 4) Applications read big lmdb files and write results to NFS shares
- 5) use NFS v3 , hard and fscache is enabled
- 6) now swap space is configured
+ 1) Applications running in Docker environment
+ 2) Application have cgroup limits --cpu-shares --memory -shm-limit
+ 3) python and C++ based applications (torch and caffe)
+ 4) Applications read big lmdb files and write results to NFS shares
+ 5) use NFS v3 , hard and fscache is enabled
+ 6) now swap space is configured
This prevents all other I/O activity on that mount to hang.
we are running into this issue more frequently and identified few
applications causing this problem.
As updated in the description, the problem seems to be happening when
exercising the stack
try_to_free_mem_cgroup_pages+0xba/0x1a0
we see this with docker containers with cgroup option --memory
<USER_SPECIFIED_MEM>.
whenever there is a deadlock, we see that the process that is hung has
reached the maximum cgroup limit, multiple times and typically cleans up
dirty data and caches to bring the usage under the limit.
This reclaim path happens many times and finally we hit probably a race
get into deadlock
** Changed in: linux (Ubuntu)
Assignee: Dragan S. (dragan-s) => Daniel Axtens (daxtens)
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https://bugs.launchpad.net/bugs/1750038
Title:
user space process hung in 'D' state waiting for disk io to complete
Status in linux package in Ubuntu:
Incomplete
Bug description:
== SRU Justification ==
[Impact]
Occasionally an application gets stuck in "D" state on NFS reads/sync and
close system calls. All the subsequent operations on the NFS mounts are stuck
and reboot is required to rectify the situation.
[Fix]
Use GPF_NOIO in some allocations in writeback to avoid a deadlock. This is
upstream in:
ae97aa524ef4 ("NFS: Use GFP_NOIO for two allocations in writeback")
[Testcase]
See Test scenario in previous description.
A test kernel with this patch was tested heavily (>100hrs of test
suite) without issue.
[Regression Potential]
This changes memory allocation in NFS to use a different policy. This could
potentially affect NFS.
However, the patch is already in Artful and Bionic without issue.
The patch does not apply to Trusty.
== Previous Description ==
Using Ubuntu Xenial user reports processes hang in D state waiting for
disk io.
Ocassionally one of the applications gets into "D" state on NFS
reads/sync and close system calls. based on the kernel backtraces
seems to be stuck in kmalloc allocation during cleanup of dirty NFS
pages.
All the subsequent operations on the NFS mounts are stuck and reboot
is required to rectify the situation.
[Test scenario]
1) Applications running in Docker environment
2) Application have cgroup limits --cpu-shares --memory -shm-limit
3) python and C++ based applications (torch and caffe)
4) Applications read big lmdb files and write results to NFS shares
5) use NFS v3 , hard and fscache is enabled
6) now swap space is configured
This prevents all other I/O activity on that mount to hang.
we are running into this issue more frequently and identified few
applications causing this problem.
As updated in the description, the problem seems to be happening when
exercising the stack
try_to_free_mem_cgroup_pages+0xba/0x1a0
we see this with docker containers with cgroup option --memory
<USER_SPECIFIED_MEM>.
whenever there is a deadlock, we see that the process that is hung has
reached the maximum cgroup limit, multiple times and typically cleans
up dirty data and caches to bring the usage under the limit.
This reclaim path happens many times and finally we hit probably a
race get into deadlock
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