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mdbx: avoid MDBX_TXN_FULL while searching for a large multi-page region.

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Resolves https://github.com/erthink/libmdbx/issues/123
but with TODO:
 - provide a user-configurable threshold instead of currently hard-coded default (MDBX_PNL_MAX/2).

Change-Id: Ia7bfd5f8d36e027444d234e3c3aabe4832313466
This commit is contained in:
Leonid Yuriev
2020-10-22 17:49:13 +03:00
parent 8a7caec54a
commit 55d190bad9
2 changed files with 23 additions and 9 deletions
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26
src/core.c
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@@ -5108,12 +5108,6 @@ skip_cache:
const unsigned wanna_range = num - 1;
while (true) { /* hsr-kick retry loop */
/* If our dirty list is already full, we can't do anything */
if (unlikely(txn->tw.dirtyroom == 0)) {
rc = MDBX_TXN_FULL;
goto fail;
}
MDBX_cursor_couple recur;
for (MDBX_cursor_op op = MDBX_FIRST;;
op = (flags & MDBX_LIFORECLAIM) ? MDBX_PREV : MDBX_NEXT) {
@@ -5154,6 +5148,11 @@ skip_cache:
}
if (op == MDBX_FIRST) { /* 1st iteration, setup cursor, etc */
if (unlikely(txn->tw.dirtyroom < txn->mt_dbs[FREE_DBI].md_depth) &&
!(txn->mt_dbistate[FREE_DBI] & DBI_DIRTY)) {
/* If our dirty list is already full, we can't touch GC */
flags &= ~MDBX_ALLOC_GC;
}
if (unlikely(!(flags & MDBX_ALLOC_GC)))
break /* reclaiming is prohibited for now */;
@@ -5264,6 +5263,21 @@ skip_cache:
goto fail;
}
const unsigned gc_len = MDBX_PNL_SIZE(gc_pnl);
/* TODO: provide a user-configurable threshold */
const unsigned threshold_2_stop_gc_reclaiming = MDBX_PNL_MAX / 2;
if (unlikely(gc_len + MDBX_PNL_SIZE(txn->tw.reclaimed_pglist) >
threshold_2_stop_gc_reclaiming)) {
/* Stop reclaiming to avoid overflow the page list.
* This is a rare case while search for a continuously multi-page region
* in a large database. https://github.com/erthink/libmdbx/issues/123 */
flags -= MDBX_ALLOC_GC;
if (unlikely(flags == 0)) {
/* Oh, we can't do anything */
rc = MDBX_TXN_FULL;
goto fail;
}
break;
}
rc = mdbx_pnl_need(&txn->tw.reclaimed_pglist, gc_len);
if (unlikely(rc != MDBX_SUCCESS))
goto fail;