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-rw-r--r--module/zfs/zio.c22
1 files changed, 19 insertions, 3 deletions
diff --git a/module/zfs/zio.c b/module/zfs/zio.c
index a721903a3..fda76123e 100644
--- a/module/zfs/zio.c
+++ b/module/zfs/zio.c
@@ -85,6 +85,22 @@ extern vmem_t *zio_alloc_arena;
extern int zfs_mg_alloc_failures;
/*
+ * The following actions directly effect the spa's sync-to-convergence logic.
+ * The values below define the sync pass when we start performing the action.
+ * Care should be taken when changing these values as they directly impact
+ * spa_sync() performance. Tuning these values may introduce subtle performance
+ * pathologies and should only be done in the context of performance analysis.
+ * These tunables will eventually be removed and replaced with #defines once
+ * enough analysis has been done to determine optimal values.
+ *
+ * The 'zfs_sync_pass_deferred_free' pass must be greater than 1 to ensure that
+ * regular blocks are not deferred.
+ */
+int zfs_sync_pass_deferred_free = 2; /* defer frees starting in this pass */
+int zfs_sync_pass_dont_compress = 5; /* don't compress starting in this pass */
+int zfs_sync_pass_rewrite = 2; /* rewrite new bps starting in this pass */
+
+/*
* An allocating zio is one that either currently has the DVA allocate
* stage set or will have it later in its lifetime.
*/
@@ -771,7 +787,7 @@ zio_free_sync(zio_t *pio, spa_t *spa, uint64_t txg, const blkptr_t *bp,
ASSERT(!BP_IS_HOLE(bp));
ASSERT(spa_syncing_txg(spa) == txg);
- ASSERT(spa_sync_pass(spa) <= SYNC_PASS_DEFERRED_FREE);
+ ASSERT(spa_sync_pass(spa) < zfs_sync_pass_deferred_free);
zio = zio_create(pio, spa, txg, bp, NULL, BP_GET_PSIZE(bp),
NULL, NULL, ZIO_TYPE_FREE, ZIO_PRIORITY_FREE, flags,
@@ -1068,7 +1084,7 @@ zio_write_bp_init(zio_t *zio)
ASSERT(zio->io_child_type == ZIO_CHILD_LOGICAL);
ASSERT(!BP_GET_DEDUP(bp));
- if (pass > SYNC_PASS_DONT_COMPRESS)
+ if (pass >= zfs_sync_pass_dont_compress)
compress = ZIO_COMPRESS_OFF;
/* Make sure someone doesn't change their mind on overwrites */
@@ -1097,7 +1113,7 @@ zio_write_bp_init(zio_t *zio)
* There should only be a handful of blocks after pass 1 in any case.
*/
if (bp->blk_birth == zio->io_txg && BP_GET_PSIZE(bp) == psize &&
- pass > SYNC_PASS_REWRITE) {
+ pass >= zfs_sync_pass_rewrite) {
enum zio_stage gang_stages = zio->io_pipeline & ZIO_GANG_STAGES;
ASSERT(psize != 0);
zio->io_pipeline = ZIO_REWRITE_PIPELINE | gang_stages;