linux-kernel - [RFC PATCH-tip 6/6] xfs: Enable reader optimistic spinning for DAX inodes

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Message-Id: <1465927959-39719-7-git-send-email-Waiman.Long@hpe.com>
Date:	Tue, 14 Jun 2016 14:12:39 -0400
From:	Waiman Long <Waiman.Long@....com>
To:	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>
Cc:	linux-kernel@...r.kernel.org, x86@...nel.org,
	linux-alpha@...r.kernel.org, linux-ia64@...r.kernel.org,
	linux-s390@...r.kernel.org, linux-arch@...r.kernel.org,
	xfs@....sgi.com, Davidlohr Bueso <dave@...olabs.net>,
	Jason Low <jason.low2@...com>,
	Dave Chinner <david@...morbit.com>,
	Scott J Norton <scott.norton@....com>,
	Douglas Hatch <doug.hatch@....com>,
	Waiman Long <Waiman.Long@....com>
Subject: [RFC PATCH-tip 6/6] xfs: Enable reader optimistic spinning for DAX inodes

This patch enables reader optimistic spinning for inodes that are
under a DAX-based mount point.

On a 4-socket Haswell machine running on a 4.7-rc1 tip-based kernel,
the fio test with multithreaded randrw and randwrite tests on the
same file on a XFS partition on top of a NVDIMM with DAX were run,
the aggregated bandwidths before and after the patch were as follows:

  Test      BW before patch     BW after patch  % change
  ----      ---------------     --------------  --------
  randrw        1352 MB/s          2164 MB/s      +60%
  randwrite     1710 MB/s          2550 MB/s      +49%

Signed-off-by: Waiman Long <Waiman.Long@....com>
---
 fs/xfs/xfs_icache.c |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/fs/xfs/xfs_icache.c b/fs/xfs/xfs_icache.c
index 99ee6ee..09f284f 100644
--- a/fs/xfs/xfs_icache.c
+++ b/fs/xfs/xfs_icache.c
@@ -71,6 +71,15 @@ xfs_inode_alloc(
 
 	mrlock_init(&ip->i_iolock, MRLOCK_BARRIER, "xfsio", ip->i_ino);
 
+	/*
+	 * Enable reader spinning for DAX nount point
+	 */
+	if (mp->m_flags & XFS_MOUNT_DAX) {
+		rwsem_set_rspin_threshold(&ip->i_iolock.mr_lock);
+		rwsem_set_rspin_threshold(&ip->i_mmaplock.mr_lock);
+		rwsem_set_rspin_threshold(&ip->i_lock.mr_lock);
+	}
+
 	/* initialise the xfs inode */
 	ip->i_ino = ino;
 	ip->i_mount = mp;
-- 
1.7.1