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ZAP: Massively switch to _by_dnode() interfaces

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Before this change ZAP called dnode_hold() for almost every block
access, that was clearly visible in profiler under heavy load, such
as BRT.  This patch makes it always hold the dnode reference between
zap_lockdir() and zap_unlockdir().  It allows to avoid most of dnode
operations between those.  It also adds several new _by_dnode() APIs
to ZAP and uses them in BRT code.  Also adds dmu_prefetch_by_dnode()
variant and uses it in the ZAP code.

After this there remains only one call to dmu_buf_dnode_enter(),
which seems to be unneeded.  So remove the call and the functions.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by:	Alexander Motin <mav@FreeBSD.org>
Sponsored by:	iXsystems, Inc.
Closes #15951
This commit is contained in:
Alexander Motin
2024-03-25 17:58:50 -04:00
committed by GitHub
parent bf8f72359d
commit 80cc516295
9 changed files with 202 additions and 172 deletions
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module/zfs/dmu.c
+14 -4
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@@ -712,8 +712,6 @@ dmu_prefetch(objset_t *os, uint64_t object, int64_t level, uint64_t offset,
uint64_t len, zio_priority_t pri)
{
dnode_t *dn;
int64_t level2 = level;
uint64_t start, end, start2, end2;
if (dmu_prefetch_max == 0 || len == 0) {
dmu_prefetch_dnode(os, object, pri);
@@ -723,6 +721,18 @@ dmu_prefetch(objset_t *os, uint64_t object, int64_t level, uint64_t offset,
if (dnode_hold(os, object, FTAG, &dn) != 0)
return;
dmu_prefetch_by_dnode(dn, level, offset, len, pri);
dnode_rele(dn, FTAG);
}
void
dmu_prefetch_by_dnode(dnode_t *dn, int64_t level, uint64_t offset,
uint64_t len, zio_priority_t pri)
{
int64_t level2 = level;
uint64_t start, end, start2, end2;
/*
* Depending on len we may do two prefetches: blocks [start, end) at
* level, and following blocks [start2, end2) at higher level2.
@@ -762,8 +772,6 @@ dmu_prefetch(objset_t *os, uint64_t object, int64_t level, uint64_t offset,
for (uint64_t i = start2; i < end2; i++)
dbuf_prefetch(dn, level2, i, pri, 0);
rw_exit(&dn->dn_struct_rwlock);
dnode_rele(dn, FTAG);
}
/*
@@ -2563,6 +2571,8 @@ EXPORT_SYMBOL(dmu_bonus_hold_by_dnode);
EXPORT_SYMBOL(dmu_buf_hold_array_by_bonus);
EXPORT_SYMBOL(dmu_buf_rele_array);
EXPORT_SYMBOL(dmu_prefetch);
EXPORT_SYMBOL(dmu_prefetch_by_dnode);
EXPORT_SYMBOL(dmu_prefetch_dnode);
EXPORT_SYMBOL(dmu_free_range);
EXPORT_SYMBOL(dmu_free_long_range);
EXPORT_SYMBOL(dmu_free_long_object);