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author | Vivek Goyal <vgoyal@redhat.com> | 2012-03-08 10:53:56 -0800 |
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committer | Jens Axboe <axboe@kernel.dk> | 2012-03-20 12:45:37 +0100 |
commit | 1cd9e039fc258f91fe38b97b3c622b13a3b8a795 (patch) | |
tree | 908f9747124b24ea4413025ab9294bd7d026b4f8 /block/blk-cgroup.h | |
parent | 671058fb2a2aac4e70f01b316b06bc59b98bd138 (diff) | |
download | lwn-1cd9e039fc258f91fe38b97b3c622b13a3b8a795.tar.gz lwn-1cd9e039fc258f91fe38b97b3c622b13a3b8a795.zip |
blkcg: alloc per cpu stats from worker thread in a delayed manner
Current per cpu stat allocation assumes GFP_KERNEL allocation flag. But in
IO path there are times when we want GFP_NOIO semantics. As there is no
way to pass the allocation flags to alloc_percpu(), this patch delays the
allocation of stats using a worker thread.
v2-> tejun suggested following changes. Changed the patch accordingly.
- move alloc_node location in structure
- reduce the size of names of some of the fields
- Reduce the scope of locking of alloc_list_lock
- Simplified stat_alloc_fn() by allocating stats for all
policies in one go and then assigning these to a group.
v3 -> Andrew suggested to put some comments in the code. Also raised
concerns about trying to allocate infinitely in case of allocation
failure. I have changed the logic to sleep for 10ms before retrying.
That should take care of non-preemptible UP kernels.
v4 -> Tejun had more suggestions.
- drop list_for_each_entry_all()
- instead of msleep() use queue_delayed_work()
- Some cleanups realted to more compact coding.
v5-> tejun suggested more cleanups leading to more compact code.
tj: - Relocated pcpu_stats into blkio_stat_alloc_fn().
- Minor comment update.
- This also fixes suspicious RCU usage warning caused by invoking
cgroup_path() from blkg_alloc() without holding RCU read lock.
Now that blkg_alloc() doesn't require sleepable context, RCU
read lock from blkg_lookup_create() is maintained throughout
blkg_alloc().
Signed-off-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-cgroup.h')
-rw-r--r-- | block/blk-cgroup.h | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/block/blk-cgroup.h b/block/blk-cgroup.h index 98cd8533378f..1de32fe0e2af 100644 --- a/block/blk-cgroup.h +++ b/block/blk-cgroup.h @@ -190,6 +190,8 @@ struct blkio_group { spinlock_t stats_lock; struct blkg_policy_data *pd[BLKIO_NR_POLICIES]; + /* List of blkg waiting for per cpu stats memory to be allocated */ + struct list_head alloc_node; struct rcu_head rcu_head; }; |