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authorTrond Myklebust <trond.myklebust@primarydata.com>2017-07-11 17:53:48 -0400
committerAnna Schumaker <Anna.Schumaker@Netapp.com>2017-07-13 16:57:18 -0400
commit301bfa483016d48b7fb9cbad87c0a04a15c25b90 (patch)
tree1e86b94a773529cae5a3144e03ff7b35f7673188 /fs
parent00422483ad415d6267d36711f0e51f4bbbd653ed (diff)
downloadlinux-stericsson-301bfa483016d48b7fb9cbad87c0a04a15c25b90.tar.gz
NFS: Don't run wake_up_bit() when nobody is waiting...
"perf lock" shows fairly heavy contention for the bit waitqueue locks when doing an I/O heavy workload. Use a bit to tell whether or not there has been contention for a lock so that we can optimise away the bit waitqueue options in those cases. Signed-off-by: Trond Myklebust <trond.myklebust@primarydata.com> Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/nfs/pagelist.c17
1 files changed, 16 insertions, 1 deletions
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 8a23e2b40b04..de9066a92c0d 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -155,9 +155,12 @@ nfs_page_group_lock(struct nfs_page *req, bool nonblock)
if (!test_and_set_bit(PG_HEADLOCK, &head->wb_flags))
return 0;
- if (!nonblock)
+ if (!nonblock) {
+ set_bit(PG_CONTENDED1, &head->wb_flags);
+ smp_mb__after_atomic();
return wait_on_bit_lock(&head->wb_flags, PG_HEADLOCK,
TASK_UNINTERRUPTIBLE);
+ }
return -EAGAIN;
}
@@ -175,6 +178,10 @@ nfs_page_group_lock_wait(struct nfs_page *req)
WARN_ON_ONCE(head != head->wb_head);
+ if (!test_bit(PG_HEADLOCK, &head->wb_flags))
+ return;
+ set_bit(PG_CONTENDED1, &head->wb_flags);
+ smp_mb__after_atomic();
wait_on_bit(&head->wb_flags, PG_HEADLOCK,
TASK_UNINTERRUPTIBLE);
}
@@ -193,6 +200,8 @@ nfs_page_group_unlock(struct nfs_page *req)
smp_mb__before_atomic();
clear_bit(PG_HEADLOCK, &head->wb_flags);
smp_mb__after_atomic();
+ if (!test_bit(PG_CONTENDED1, &head->wb_flags))
+ return;
wake_up_bit(&head->wb_flags, PG_HEADLOCK);
}
@@ -383,6 +392,8 @@ void nfs_unlock_request(struct nfs_page *req)
smp_mb__before_atomic();
clear_bit(PG_BUSY, &req->wb_flags);
smp_mb__after_atomic();
+ if (!test_bit(PG_CONTENDED2, &req->wb_flags))
+ return;
wake_up_bit(&req->wb_flags, PG_BUSY);
}
@@ -465,6 +476,10 @@ void nfs_release_request(struct nfs_page *req)
int
nfs_wait_on_request(struct nfs_page *req)
{
+ if (!test_bit(PG_BUSY, &req->wb_flags))
+ return 0;
+ set_bit(PG_CONTENDED2, &req->wb_flags);
+ smp_mb__after_atomic();
return wait_on_bit_io(&req->wb_flags, PG_BUSY,
TASK_UNINTERRUPTIBLE);
}