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Commit b4f937cf authored by Trond Myklebust's avatar Trond Myklebust Committed by Anna Schumaker
Browse files

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: default avatarTrond Myklebust <trond.myklebust@primarydata.com>
Signed-off-by: default avatarAnna Schumaker <Anna.Schumaker@Netapp.com>
parent 20fa1902

fs/nfs/pagelist.c

+16 −1
Original line number Diff line number Diff line
@@ -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);

}

include/linux/nfs_page.h

+2 −0
Original line number Diff line number Diff line
@@ -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;