From 05b3eb6d232009db247882a39d518e7282630753 Mon Sep 17 00:00:00 2001 From: Brian Behlendorf Date: Tue, 30 Nov 2021 10:38:09 -0800 Subject: Default to zfs_dmu_offset_next_sync=1 Strict hole reporting was previously disabled by default as a performance optimization. However, this has lead to confusion over the expected behavior and a variety of workarounds being adopted by consumers of ZFS. Change the default behavior to always report holes and force the TXG sync. Reviewed-by: Matthew Ahrens Reviewed-by: Tony Hutter Signed-off-by: Brian Behlendorf Closes #12746 --- module/zfs/dmu.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-) (limited to 'module/zfs/dmu.c') diff --git a/module/zfs/dmu.c b/module/zfs/dmu.c index eee3e70bb..5ce11e86d 100644 --- a/module/zfs/dmu.c +++ b/module/zfs/dmu.c @@ -73,9 +73,13 @@ int zfs_nopwrite_enabled = 1; unsigned long zfs_per_txg_dirty_frees_percent = 5; /* - * Enable/disable forcing txg sync when dirty in dmu_offset_next. + * Enable/disable forcing txg sync when dirty checking for holes with lseek(). + * By default this is enabled to ensure accurate hole reporting, it can result + * in a significant performance penalty for lseek(SEEK_HOLE) heavy workloads. + * Disabling this option will result in holes never being reported in dirty + * files which is always safe. */ -int zfs_dmu_offset_next_sync = 0; +int zfs_dmu_offset_next_sync = 1; /* * Limit the amount we can prefetch with one call to this amount. This @@ -2107,8 +2111,8 @@ restart: * If the zfs_dmu_offset_next_sync module option is enabled * then strict hole reporting has been requested. Dirty * dnodes must be synced to disk to accurately report all - * holes. When disabled (the default) dirty dnodes are - * reported to not have any holes which is always safe. + * holes. When disabled dirty dnodes are reported to not + * have any holes which is always safe. * * When called by zfs_holey_common() the zp->z_rangelock * is held to prevent zfs_write() and mmap writeback from -- cgit v1.2.3