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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
Download Patch File Download Diff File Expand all files Collapse all files
module/zfs/dsl_dataset.c
+4 -6
View File
@@ -192,9 +192,8 @@ dsl_dataset_block_born(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx)
}
mutex_exit(&ds->ds_lock);
dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD, delta,
compressed, uncompressed, tx);
dsl_dir_transfer_space(ds->ds_dir, used - delta,
dsl_dir_diduse_transfer_space(ds->ds_dir, delta,
compressed, uncompressed, used,
DD_USED_REFRSRV, DD_USED_HEAD, tx);
}
@@ -291,9 +290,8 @@ dsl_dataset_block_kill(dsl_dataset_t *ds, const blkptr_t *bp, dmu_tx_t *tx,
delta = parent_delta(ds, -used);
dsl_dataset_phys(ds)->ds_unique_bytes -= used;
mutex_exit(&ds->ds_lock);
dsl_dir_diduse_space(ds->ds_dir, DD_USED_HEAD,
delta, -compressed, -uncompressed, tx);
dsl_dir_transfer_space(ds->ds_dir, -used - delta,
dsl_dir_diduse_transfer_space(ds->ds_dir,
delta, -compressed, -uncompressed, -used,
DD_USED_REFRSRV, DD_USED_HEAD, tx);
} else {
dprintf_bp(bp, "putting on dead list: %s", "");