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bdrv_change_aio_context: use hash table instead of list of visited nodes

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Minor performance improvement, but given that we have hash tables
available, avoid iterating in the visited nodes list every time just
to check if a node has been already visited.

The data structure is not actually a proper hash map, but an hash set,
as we are just adding nodes and not key,value pairs.

Suggested-by: Hanna Reitz <hreitz@redhat.com>
Signed-off-by: Emanuele Giuseppe Esposito <eesposit@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Message-Id: <20221025084952.2139888-4-eesposit@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Emanuele Giuseppe Esposito 2022-10-25 04:49:45 -04:00 committed by Kevin Wolf
parent 7e8c182fb5
commit e08cc001d5
3 changed files with 19 additions and 14 deletions
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28
block.c
View File

@ -105,7 +105,7 @@ static void bdrv_reopen_abort(BDRVReopenState *reopen_state);
static bool bdrv_backing_overridden(BlockDriverState *bs);
static bool bdrv_change_aio_context(BlockDriverState *bs, AioContext *ctx,
GSList **visited, Transaction *tran,
GHashTable *visited, Transaction *tran,
Error **errp);
/* If non-zero, use only whitelisted block drivers */
@ -7315,14 +7315,15 @@ typedef struct BdrvStateSetAioContext {
} BdrvStateSetAioContext;
static bool bdrv_parent_change_aio_context(BdrvChild *c, AioContext *ctx,
GSList **visited, Transaction *tran,
GHashTable *visited,
Transaction *tran,
Error **errp)
{
GLOBAL_STATE_CODE();
if (g_slist_find(*visited, c)) {
if (g_hash_table_contains(visited, c)) {
return true;
}
*visited = g_slist_prepend(*visited, c);
g_hash_table_add(visited, c);
/*
* A BdrvChildClass that doesn't handle AioContext changes cannot
@ -7353,14 +7354,14 @@ bool bdrv_child_can_set_aio_context(BdrvChild *c, AioContext *ctx,
}
bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx,
GSList **visited, Transaction *tran,
GHashTable *visited, Transaction *tran,
Error **errp)
{
GLOBAL_STATE_CODE();
if (g_slist_find(*visited, c)) {
if (g_hash_table_contains(visited, c)) {
return true;
}
*visited = g_slist_prepend(*visited, c);
g_hash_table_add(visited, c);
return bdrv_change_aio_context(c->bs, ctx, visited, tran, errp);
}
@ -7445,7 +7446,7 @@ static TransactionActionDrv set_aio_context = {
* responsible for freeing the list afterwards.
*/
static bool bdrv_change_aio_context(BlockDriverState *bs, AioContext *ctx,
GSList **visited, Transaction *tran,
GHashTable *visited, Transaction *tran,
Error **errp)
{
BdrvChild *c;
@ -7524,7 +7525,7 @@ int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
BdrvChild *ignore_child, Error **errp)
{
Transaction *tran;
GSList *visited;
GHashTable *visited;
int ret;
AioContext *old_context = bdrv_get_aio_context(bs);
GLOBAL_STATE_CODE();
@ -7536,9 +7537,12 @@ int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
* is successful (the transaction itself).
*/
tran = tran_new();
visited = ignore_child ? g_slist_prepend(NULL, ignore_child) : NULL;
ret = bdrv_change_aio_context(bs, ctx, &visited, tran, errp);
g_slist_free(visited);
visited = g_hash_table_new(NULL, NULL);
if (ignore_child) {
g_hash_table_add(visited, ignore_child);
}
ret = bdrv_change_aio_context(bs, ctx, visited, tran, errp);
g_hash_table_destroy(visited);
/*
* Linear phase: go through all callbacks collected in the transaction.

2
include/block/block-global-state.h
View File

@ -233,7 +233,7 @@ bool bdrv_can_set_aio_context(BlockDriverState *bs, AioContext *ctx,
AioContext *bdrv_child_get_parent_aio_context(BdrvChild *c);
bool bdrv_child_change_aio_context(BdrvChild *c, AioContext *ctx,
GSList **visited, Transaction *tran,
GHashTable *visited, Transaction *tran,
Error **errp);
int bdrv_child_try_change_aio_context(BlockDriverState *bs, AioContext *ctx,
BdrvChild *ignore_child, Error **errp);

3
include/block/block_int-common.h
View File

@ -911,7 +911,8 @@ struct BdrvChildClass {
void (*set_aio_ctx)(BdrvChild *child, AioContext *ctx, GSList **ignore);
bool (*change_aio_ctx)(BdrvChild *child, AioContext *ctx,
GSList **visited, Transaction *tran, Error **errp);
GHashTable *visited, Transaction *tran,
Error **errp);
AioContext *(*get_parent_aio_context)(BdrvChild *child);