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Introduce dsl_dir_diduse_transfer_space()

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Most of dsl_dir_diduse_space() and dsl_dir_transfer_space() CPU time
is a dd_lock overhead and time spent in dmu_buf_will_dirty(). Calling
them one after another is a waste of time and even more contention.
Doing that twice for each rewritten block within dbuf_write_done()
via dsl_dataset_block_kill() and dsl_dataset_block_born() created one
of the biggest CPU overheads in case of small blocks rewrite.

dsl_dir_diduse_transfer_space() combines functionality of these two
functions for cases where it is needed, but without double overhead,
practically for the cost of dsl_dir_diduse_space() or even cheaper.

While there, optimize dsl_dir_phys() calls in dsl_dir_diduse_space()
and dsl_dir_transfer_space().  It seems Clang detects some aliasing
there, repeating dd->dd_dbuf->db_data dereference multiple times,
increasing dd_lock scope and contention.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Matthew Ahrens <mahrens@delphix.com>
Author: Ryan Moeller <ryan@iXsystems.com>
Signed-off-by: Alexander Motin <mav@FreeBSD.org>
Closes #12300
This commit is contained in:
Alexander Motin
2021-07-16 15:39:24 -04:00
committed by Tony Hutter
parent 968dc13572
commit ba76bb30a6
3 changed files with 85 additions and 38 deletions
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include/sys/dsl_dir.h
+3
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@@ -174,6 +174,9 @@ void dsl_dir_diduse_space(dsl_dir_t *dd, dd_used_t type,
int64_t used, int64_t compressed, int64_t uncompressed, dmu_tx_t *tx);
void dsl_dir_transfer_space(dsl_dir_t *dd, int64_t delta,
dd_used_t oldtype, dd_used_t newtype, dmu_tx_t *tx);
void dsl_dir_diduse_transfer_space(dsl_dir_t *dd, int64_t used,
int64_t compressed, int64_t uncompressed, int64_t tonew,
dd_used_t oldtype, dd_used_t newtype, dmu_tx_t *tx);
int dsl_dir_set_quota(const char *ddname, zprop_source_t source,
uint64_t quota);
int dsl_dir_set_reservation(const char *ddname, zprop_source_t source,