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Illumos #3552, #3564

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3552 condensing one space map burns 3 seconds of CPU in spa_sync() thread
3564 spa_sync() spends 5-10% of its time in metaslab_sync() (when not condensing)
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Dan Kimmel <dan.kimmel@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Approved by: Richard Lowe <richlowe@richlowe.net>

References:
  illumos/illumos-gate@16a4a80742
  https://www.illumos.org/issues/3552
  https://www.illumos.org/issues/3564

Ported-by: Tim Chase <tim@chase2k.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #1513
This commit is contained in:
George Wilson
2013-06-14 22:30:35 -05:00
committed by Brian Behlendorf
parent c99c90015e
commit e51be06697
6 changed files with 327 additions and 112 deletions
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include/sys/metaslab_impl.h
+25 -7
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@@ -67,20 +67,38 @@ struct metaslab_group {
};
/*
* Each metaslab's free space is tracked in space map object in the MOS,
* which is only updated in syncing context. Each time we sync a txg,
* Each metaslab maintains an in-core free map (ms_map) that contains the
* current list of free segments. As blocks are allocated, the allocated
* segment is removed from the ms_map and added to a per txg allocation map.
* As blocks are freed, they are added to the per txg free map. These per
* txg maps allow us to process all allocations and frees in syncing context
* where it is safe to update the on-disk space maps.
*
* Each metaslab's free space is tracked in a space map object in the MOS,
* which is only updated in syncing context. Each time we sync a txg,
* we append the allocs and frees from that txg to the space map object.
* When the txg is done syncing, metaslab_sync_done() updates ms_smo
* to ms_smo_syncing. Everything in ms_smo is always safe to allocate.
* to ms_smo_syncing. Everything in ms_smo is always safe to allocate.
*
* To load the in-core free map we read the space map object from disk.
* This object contains a series of alloc and free records that are
* combined to make up the list of all free segments in this metaslab. These
* segments are represented in-core by the ms_map and are stored in an
* AVL tree.
*
* As the space map objects grows (as a result of the appends) it will
* eventually become space-inefficient. When the space map object is
* zfs_condense_pct/100 times the size of the minimal on-disk representation,
* we rewrite it in its minimized form.
*/
struct metaslab {
kmutex_t ms_lock; /* metaslab lock */
space_map_obj_t ms_smo; /* synced space map object */
space_map_obj_t ms_smo_syncing; /* syncing space map object */
space_map_t ms_allocmap[TXG_SIZE]; /* allocated this txg */
space_map_t ms_freemap[TXG_SIZE]; /* freed this txg */
space_map_t ms_defermap[TXG_DEFER_SIZE]; /* deferred frees */
space_map_t ms_map; /* in-core free space map */
space_map_t *ms_allocmap[TXG_SIZE]; /* allocated this txg */
space_map_t *ms_freemap[TXG_SIZE]; /* freed this txg */
space_map_t *ms_defermap[TXG_DEFER_SIZE]; /* deferred frees */
space_map_t *ms_map; /* in-core free space map */
int64_t ms_deferspace; /* sum of ms_defermap[] space */
uint64_t ms_weight; /* weight vs. others in group */
metaslab_group_t *ms_group; /* metaslab group */