From f18c9a9030972d892a244968c653aceb98e27c70 Mon Sep 17 00:00:00 2001 From: Dave Chinner Date: Wed, 20 May 2020 13:17:11 -0700 Subject: xfs: reduce free inode accounting overhead Shaokun Zhang reported that XFS was using substantial CPU time in percpu_count_sum() when running a single threaded benchmark on a high CPU count (128p) machine from xfs_mod_ifree(). The issue is that the filesystem is empty when the benchmark runs, so inode allocation is running with a very low inode free count. With the percpu counter batching, this means comparisons when the counter is less that 128 * 256 = 32768 use the slow path of adding up all the counters across the CPUs, and this is expensive on high CPU count machines. The summing in xfs_mod_ifree() is only used to fire an assert if an underrun occurs. The error is ignored by the higher level code. Hence this is really just debug code and we don't need to run it on production kernels, nor do we need such debug checks to return error values just to trigger an assert. Finally, xfs_mod_icount/xfs_mod_ifree are only called from xfs_trans_unreserve_and_mod_sb(), so get rid of them and just directly call the percpu_counter_add/percpu_counter_compare functions. The compare functions are now run only on debug builds as they are internal to ASSERT() checks and so only compiled in when ASSERTs are active (CONFIG_XFS_DEBUG=y or CONFIG_XFS_WARN=y). Reported-by: Shaokun Zhang Signed-off-by: Dave Chinner Reviewed-by: Christoph Hellwig Reviewed-by: Darrick J. Wong Signed-off-by: Darrick J. Wong --- fs/xfs/xfs_mount.c | 33 --------------------------------- 1 file changed, 33 deletions(-) (limited to 'fs/xfs/xfs_mount.c') diff --git a/fs/xfs/xfs_mount.c b/fs/xfs/xfs_mount.c index bb91f04266b9..d5dcf9869860 100644 --- a/fs/xfs/xfs_mount.c +++ b/fs/xfs/xfs_mount.c @@ -1189,39 +1189,6 @@ xfs_log_sbcount(xfs_mount_t *mp) return xfs_sync_sb(mp, true); } -/* - * Deltas for the inode count are +/-64, hence we use a large batch size - * of 128 so we don't need to take the counter lock on every update. - */ -#define XFS_ICOUNT_BATCH 128 -int -xfs_mod_icount( - struct xfs_mount *mp, - int64_t delta) -{ - percpu_counter_add_batch(&mp->m_icount, delta, XFS_ICOUNT_BATCH); - if (__percpu_counter_compare(&mp->m_icount, 0, XFS_ICOUNT_BATCH) < 0) { - ASSERT(0); - percpu_counter_add(&mp->m_icount, -delta); - return -EINVAL; - } - return 0; -} - -int -xfs_mod_ifree( - struct xfs_mount *mp, - int64_t delta) -{ - percpu_counter_add(&mp->m_ifree, delta); - if (percpu_counter_compare(&mp->m_ifree, 0) < 0) { - ASSERT(0); - percpu_counter_add(&mp->m_ifree, -delta); - return -EINVAL; - } - return 0; -} - /* * Deltas for the block count can vary from 1 to very large, but lock contention * only occurs on frequent small block count updates such as in the delayed -- cgit v1.2.3-58-ga151