Re: NFS: 82ms wakeup latency 4.14-rc4

[Mike Galbraith <efault@gmx.de>]

On Mon, 2017-12-18 at 16:17 +0100, Mike Galbraith wrote:
> 
> ....
> kworker/-7421    0.N.. 82893us : nfs_release_request <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82893us : nfs_unlock_and_release_request <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82893us : nfs_unlock_request <-nfs_unlock_and_release_request
> kworker/-7421    0.N.. 82893us : nfs_page_group_destroy <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82893us : nfs_page_group_sync_on_bit <-nfs_page_group_destroy
> kworker/-7421    0.N.. 82893us : nfs_page_group_lock <-nfs_page_group_sync_on_bit
> kworker/-7421    0.N.. 82893us : nfs_page_group_unlock <-nfs_page_group_sync_on_bit
> kworker/-7421    0.N.. 82893us : nfs_free_request <-nfs_page_group_destroy
> kworker/-7421    0.N.. 82893us : nfs_put_lock_context <-nfs_free_request
> kworker/-7421    0.N.. 82893us : put_nfs_open_context <-nfs_free_request
> kworker/-7421    0.N.. 82893us : __put_nfs_open_context <-nfs_free_request
> kworker/-7421    0.N.. 82894us : kmem_cache_free <-nfs_page_group_destroy
> kworker/-7421    0.N.. 82894us : __slab_free <-kmem_cache_free
> kworker/-7421    0.N.. 82894us : clear_wb_congested <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82894us : nfs_init_cinfo <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82894us : nfs_init_cinfo_from_inode <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82894us : nfs_commit_end <-nfs_commit_release_pages
> kworker/-7421    0.N.. 82894us : nfs_commitdata_release <-rpc_free_task
> kworker/-7421    0.N.. 82894us : put_nfs_open_context <-nfs_commitdata_release
> kworker/-7421    0.N.. 82894us : __put_nfs_open_context <-nfs_commitdata_release
> kworker/-7421    0.N.. 82895us : mempool_free <-rpc_free_task
> kworker/-7421    0.N.. 82895us : mempool_free_slab <-rpc_free_task
> kworker/-7421    0.N.. 82895us : kmem_cache_free <-rpc_free_task
> kworker/-7421    0.N.. 82895us : ___might_sleep <-process_one_work
> kworker/-7421    0.N.. 82895us : _cond_resched <-process_one_work
> kworker/-7421    0dN.1 82895us : rcu_note_context_switch <-__schedule

diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index d0543e19098a..b42bf3b21e05 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -428,6 +428,7 @@ void nfs_free_request(struct nfs_page *req)
 	/* Release struct file and open context */
 	nfs_clear_request(req);
 	nfs_page_free(req);
+	cond_resched();
 }
 
 void nfs_release_request(struct nfs_page *req)