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Conserve stack in dsl_scan_visitbp() 

The recursive call chain dsl_scan_visitbp() -> dsl_scan_recurse() ->
dsl_scan_visitdnode() -> dsl_scan_visitbp has been observed to consume
considerable stack resulting in a stack overflow (>8k).  The cleanest
way I see to fix this with minimal impact to the existing flow of
code, and with the fewest performance concerns, is to always inline
dsl_scan_recurse() and dsl_scan_visitdnode().  While this will increase
the function size of dsl_scan_visitbp(), by 4660 bytes, it also reduces
the stack requirements by removing the function call overhead.

Issue #174
This commit is contained in:
Brian Behlendorf 2011-04-22 10:12:49 -07:00
parent 44e9e34793
commit 7a060636b0
1 changed files with 2 additions and 2 deletions
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4
module/zfs/dsl_scan.c
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@ -648,7 +648,7 @@ dsl_scan_check_resume(dsl_scan_t *scn, const dnode_phys_t *dnp,
* Return nonzero on i/o error.
* Return new buf to write out in *bufp.
*/
static int
__attribute__((always_inline)) static int
dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
dnode_phys_t *dnp, const blkptr_t *bp,
const zbookmark_t *zb, dmu_tx_t *tx, arc_buf_t **bufp)
@ -754,7 +754,7 @@ dsl_scan_recurse(dsl_scan_t *scn, dsl_dataset_t *ds, dmu_objset_type_t ostype,
return (0);
}
static void
__attribute__((always_inline)) static void
dsl_scan_visitdnode(dsl_scan_t *scn, dsl_dataset_t *ds,
dmu_objset_type_t ostype, dnode_phys_t *dnp, arc_buf_t *buf,
uint64_t object, dmu_tx_t *tx)