c/mirror_zfs
1
0
Fork 0
mirror of https://git.proxmox.com/git/mirror_zfs.git synced 2026-05-22 02:27:36 +03:00
Code Issues Packages Projects Releases Wiki Activity

OpenZFS 7613 - ms_freetree[4] is only used in syncing context

Browse Source 
metaslab_t:ms_freetree[TXG_SIZE] is only used in syncing context. We
should replace it with two trees: the freeing tree (ranges that we are
freeing this syncing txg) and the freed tree (ranges which have been
freed this txg).

Authored by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Alex Reece <alex@delphix.com>
Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Ported-by: Tim Chase <tim@chase2k.com>

OpenZFS-issue: https://www.illumos.org/issues/7613
OpenZFS-commit: https://github.com/openzfs/openzfs/commit/a8698da2
Closes #5598
This commit is contained in:
Tim Chase
2017-01-26 17:27:19 -06:00
committed by Brian Behlendorf
parent 9c9531cb6f
commit 258553d3d7
2 changed files with 82 additions and 76 deletions
Download Patch File Download Diff File Expand all files Collapse all files
include/sys/metaslab_impl.h
+44 -33
View File
@@ -254,21 +254,24 @@ struct metaslab_group {
#define MAX_LBAS 64
/*
* Each metaslab maintains a set of in-core trees to track metaslab operations.
* The in-core free tree (ms_tree) contains the current list of free segments.
* As blocks are allocated, the allocated segment are removed from the ms_tree
* and added to a per txg allocation tree (ms_alloctree). As blocks are freed,
* they are added to the per txg free tree (ms_freetree). These per txg
* trees allow us to process all allocations and frees in syncing context
* where it is safe to update the on-disk space maps. One additional in-core
* tree is maintained to track deferred frees (ms_defertree). Once a block
* is freed it will move from the ms_freetree to the ms_defertree. A deferred
* free means that a block has been freed but cannot be used by the pool
* until TXG_DEFER_SIZE transactions groups later. For example, a block
* that is freed in txg 50 will not be available for reallocation until
* txg 52 (50 + TXG_DEFER_SIZE). This provides a safety net for uberblock
* rollback. A pool could be safely rolled back TXG_DEFERS_SIZE
* transactions groups and ensure that no block has been reallocated.
* Each metaslab maintains a set of in-core trees to track metaslab
* operations. The in-core free tree (ms_tree) contains the list of
* free segments which are eligible for allocation. As blocks are
* allocated, the allocated segments are removed from the ms_tree and
* added to a per txg allocation tree (ms_alloctree). This allows us to
* process all allocations in syncing context where it is safe to update
* the on-disk space maps. Frees are also processed in syncing context.
* Most frees are generated from syncing context, and those that are not
* are held in the spa_free_bplist for processing in syncing context.
* An additional set of in-core trees is maintained to track deferred
* frees (ms_defertree). Once a block is freed it will move from the
* ms_freedtree to the ms_defertree. A deferred free means that a block
* has been freed but cannot be used by the pool until TXG_DEFER_SIZE
* transactions groups later. For example, a block that is freed in txg
* 50 will not be available for reallocation until txg 52 (50 +
* TXG_DEFER_SIZE). This provides a safety net for uberblock rollback.
* A pool could be safely rolled back TXG_DEFERS_SIZE transactions
* groups and ensure that no block has been reallocated.
*
* The simplified transition diagram looks like this:
*
@@ -276,33 +279,34 @@ struct metaslab_group {
* ALLOCATE
* |
* V
* free segment (ms_tree) --------> ms_alloctree ----> (write to space map)
* free segment (ms_tree) -----> ms_alloctree[4] ----> (write to space map)
* ^
* |
* | ms_freetree <--- FREE
* | ms_freeingtree <--- FREE
* | |
* | v
* | ms_freedtree
* | |
* | |
* +----------- ms_defertree <-------+---------> (write to space map)
* +-------- ms_defertree[2] <-------+---------> (write to space map)
*
*
* Each metaslab's space is tracked in a single space map 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.
* The pool space is only updated once all metaslabs have finished syncing.
* 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. The
* pool space is only updated once all metaslabs have finished syncing.
*
* To load the in-core free tree we read the space map 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
* To load the in-core free tree we read the space map 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_tree and are stored in an
* AVL tree.
*
* As the space map grows (as a result of the appends) it will
* eventually become space-inefficient. When the metaslab's in-core free tree
* is zfs_condense_pct/100 times the size of the minimal on-disk
* representation, we rewrite it in its minimized form. If a metaslab
* needs to condense then we must set the ms_condensing flag to ensure
* that allocations are not performed on the metaslab that is being written.
* eventually become space-inefficient. When the metaslab's in-core
* free tree is zfs_condense_pct/100 times the size of the minimal
* on-disk representation, we rewrite it in its minimized form. If a
* metaslab needs to condense then we must set the ms_condensing flag to
* ensure that allocations are not performed on the metaslab that is
* being written.
*/
struct metaslab {
kmutex_t ms_lock;
@@ -314,10 +318,17 @@ struct metaslab {
uint64_t ms_fragmentation;
range_tree_t *ms_alloctree[TXG_SIZE];
range_tree_t *ms_freetree[TXG_SIZE];
range_tree_t *ms_defertree[TXG_DEFER_SIZE];
range_tree_t *ms_tree;
/*
* The following range trees are accessed only from syncing context.
* ms_free*tree only have entries while syncing, and are empty
* between syncs.
*/
range_tree_t *ms_freeingtree; /* to free this syncing txg */
range_tree_t *ms_freedtree; /* already freed this syncing txg */
range_tree_t *ms_defertree[TXG_DEFER_SIZE];
boolean_t ms_condensing; /* condensing? */
boolean_t ms_condense_wanted;