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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 17:12:07 -0400
commitb4f937cffa66b3d56eb8f586e620d0b223a281a3 (patch)
tree1e86b94a773529cae5a3144e03ff7b35f7673188
parent20fa19027286983ab2734b5910c4a687436e0c31 (diff)
download96b-common-b4f937cffa66b3d56eb8f586e620d0b223a281a3.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>
-rw-r--r--fs/nfs/pagelist.c17
-rw-r--r--include/linux/nfs_page.h2
2 files changed, 18 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);
}
diff --git a/include/linux/nfs_page.h b/include/linux/nfs_page.h
index abbee2d15dce..d67b67ae6c8b 100644
--- a/include/linux/nfs_page.h
+++ b/include/linux/nfs_page.h
@@ -33,6 +33,8 @@ enum {
PG_UPTODATE, /* page group sync bit in read path */
PG_WB_END, /* page group sync bit in write path */
PG_REMOVE, /* page group sync bit in write path */
+ PG_CONTENDED1, /* Is someone waiting for a lock? */
+ PG_CONTENDED2, /* Is someone waiting for a lock? */
};
struct nfs_inode;