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Use the new "Slab" context for some allocations in reorderbuffer.h.

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Note that this change alone does not yet fully address the performance
problems triggering this work, a large portion of the slowdown is
triggered by the tuple allocator, which isn't converted to the new
allocator.  It would be possible to do so, but using evenly sized
objects, like both the current implementation in reorderbuffer.c and
slab.c, wastes a fair amount of memory.  A later patch by Tomas will
introduce a better approach.

Author: Tomas Vondra
Reviewed-By: Andres Freund
Discussion: https://postgr.es/m/d15dff83-0b37-28ed-0809-95a5cc7292ad@2ndquadrant.com
This commit is contained in:
Andres Freund 2017-02-27 03:41:44 -08:00
parent 58b25e9810
commit 9fab40ad32
2 changed files with 22 additions and 66 deletions
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66
src/backend/replication/logical/reorderbuffer.c
View File

@ -156,10 +156,7 @@ static const Size max_changes_in_memory = 4096;
* major bottleneck, especially when spilling to disk while decoding batch
* workloads.
*/
static const Size max_cached_changes = 4096 * 2;
static const Size max_cached_tuplebufs = 4096 * 2; /* ~8MB */
static const Size max_cached_transactions = 512;
/* ---------------------------------------
* primary reorderbuffer support routines
@ -241,6 +238,16 @@ ReorderBufferAllocate(void)
buffer->context = new_ctx;
buffer->change_context = SlabContextCreate(new_ctx,
"Change",
SLAB_DEFAULT_BLOCK_SIZE,
sizeof(ReorderBufferChange));
buffer->txn_context = SlabContextCreate(new_ctx,
"TXN",
SLAB_DEFAULT_BLOCK_SIZE,
sizeof(ReorderBufferTXN));
hash_ctl.keysize = sizeof(TransactionId);
hash_ctl.entrysize = sizeof(ReorderBufferTXNByIdEnt);
hash_ctl.hcxt = buffer->context;
@ -251,8 +258,6 @@ ReorderBufferAllocate(void)
buffer->by_txn_last_xid = InvalidTransactionId;
buffer->by_txn_last_txn = NULL;
buffer->nr_cached_transactions = 0;
buffer->nr_cached_changes = 0;
buffer->nr_cached_tuplebufs = 0;
buffer->outbuf = NULL;
@ -261,8 +266,6 @@ ReorderBufferAllocate(void)
buffer->current_restart_decoding_lsn = InvalidXLogRecPtr;
dlist_init(&buffer->toplevel_by_lsn);
dlist_init(&buffer->cached_transactions);
dlist_init(&buffer->cached_changes);
slist_init(&buffer->cached_tuplebufs);
return buffer;
@ -291,19 +294,8 @@ ReorderBufferGetTXN(ReorderBuffer *rb)
{
ReorderBufferTXN *txn;
/* check the slab cache */
if (rb->nr_cached_transactions > 0)
{
rb->nr_cached_transactions--;
txn = (ReorderBufferTXN *)
dlist_container(ReorderBufferTXN, node,
dlist_pop_head_node(&rb->cached_transactions));
}
else
{
txn = (ReorderBufferTXN *)
MemoryContextAlloc(rb->context, sizeof(ReorderBufferTXN));
}
MemoryContextAlloc(rb->txn_context, sizeof(ReorderBufferTXN));
memset(txn, 0, sizeof(ReorderBufferTXN));
@ -344,19 +336,8 @@ ReorderBufferReturnTXN(ReorderBuffer *rb, ReorderBufferTXN *txn)
txn->invalidations = NULL;
}
/* check whether to put into the slab cache */
if (rb->nr_cached_transactions < max_cached_transactions)
{
rb->nr_cached_transactions++;
dlist_push_head(&rb->cached_transactions, &txn->node);
VALGRIND_MAKE_MEM_UNDEFINED(txn, sizeof(ReorderBufferTXN));
VALGRIND_MAKE_MEM_DEFINED(&txn->node, sizeof(txn->node));
}
else
{
pfree(txn);
}
}
/*
* Get an unused, possibly preallocated, ReorderBufferChange.
@ -366,19 +347,8 @@ ReorderBufferGetChange(ReorderBuffer *rb)
{
ReorderBufferChange *change;
/* check the slab cache */
if (rb->nr_cached_changes)
{
rb->nr_cached_changes--;
change = (ReorderBufferChange *)
dlist_container(ReorderBufferChange, node,
dlist_pop_head_node(&rb->cached_changes));
}
else
{
change = (ReorderBufferChange *)
MemoryContextAlloc(rb->context, sizeof(ReorderBufferChange));
}
MemoryContextAlloc(rb->change_context, sizeof(ReorderBufferChange));
memset(change, 0, sizeof(ReorderBufferChange));
return change;
@ -434,20 +404,8 @@ ReorderBufferReturnChange(ReorderBuffer *rb, ReorderBufferChange *change)
break;
}
/* check whether to put into the slab cache */
if (rb->nr_cached_changes < max_cached_changes)
{
rb->nr_cached_changes++;
dlist_push_head(&rb->cached_changes, &change->node);
VALGRIND_MAKE_MEM_UNDEFINED(change, sizeof(ReorderBufferChange));
VALGRIND_MAKE_MEM_DEFINED(&change->node, sizeof(change->node));
}
else
{
pfree(change);
}
}
/*
* Get an unused, possibly preallocated, ReorderBufferTupleBuf fitting at

14
src/include/replication/reorderbuffer.h
View File

@ -330,6 +330,12 @@ struct ReorderBuffer
*/
MemoryContext context;
/*
* Memory contexts for specific types objects
*/
MemoryContext change_context;
MemoryContext txn_context;
/*
* Data structure slab cache.
*
@ -340,14 +346,6 @@ struct ReorderBuffer
* on top of reorderbuffer.c
*/
/* cached ReorderBufferTXNs */
dlist_head cached_transactions;
Size nr_cached_transactions;
/* cached ReorderBufferChanges */
dlist_head cached_changes;
Size nr_cached_changes;
/* cached ReorderBufferTupleBufs */
slist_head cached_tuplebufs;
Size nr_cached_tuplebufs;