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ExtentWalker: increase efficiency for typical btrfs extent sizes

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Perf was blaming more than 50% of cycles on TREE_SEARCH_V2.  strace
showed 4 TREE_SEARCH_V2 calls for every pread in grow_backward().

Fix by increasing the extent fetch batch size so it is more likely
to include the desired items in the first fetch attempt.

This removes TREE_SEARCH_V2 from the top 10 list of cycle consumers.

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell
2018-01-28 01:37:21 -05:00
parent e74c0a9d80
commit 72cc9c2b60
1 changed files with 1 additions and 1 deletions
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2
include/crucible/extentwalker.h
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@@ -58,7 +58,7 @@ namespace crucible {
virtual Vec get_extent_map(off_t pos); virtual Vec get_extent_map(off_t pos);
static const unsigned sc_extent_fetch_max = 64; static const unsigned sc_extent_fetch_max = 1024;
static const unsigned sc_extent_fetch_min = 4; static const unsigned sc_extent_fetch_min = 4;
static const off_t sc_step_size = 0x1000 * (sc_extent_fetch_max / 2); static const off_t sc_step_size = 0x1000 * (sc_extent_fetch_max / 2);