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[Qemu-block] [PATCH v1 13/18] block/pcache: inflight readahead request w
From: |
Pavel Butsykin |
Subject: |
[Qemu-block] [PATCH v1 13/18] block/pcache: inflight readahead request waiting for aio read |
Date: |
Tue, 15 Nov 2016 09:37:10 +0300 |
If there was a cache hit, but the status of the node is NODE_STATUS_INFLIGHT,
then this means that a readahead request for this node is in flight. In this
case,
we can wait for the completion of the readahead request, and then copy the
data. It allows us even more to optimize aio read requests.
Signed-off-by: Pavel Butsykin <address@hidden>
---
block/pcache.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++-------
1 file changed, 65 insertions(+), 8 deletions(-)
diff --git a/block/pcache.c b/block/pcache.c
index 0f918d0..55d1061 100644
--- a/block/pcache.c
+++ b/block/pcache.c
@@ -67,9 +67,15 @@ typedef struct BDRVPCacheState {
uint64_t readahead_size;
} BDRVPCacheState;
+typedef struct ACBLinkEntry {
+ QTAILQ_ENTRY(ACBLinkEntry) entry;
+ struct PCacheAIOCBRead *acb;
+} ACBLinkEntry;
+
typedef struct PCacheNode {
RBCacheNode common;
uint8_t *data;
+ QTAILQ_HEAD(, ACBLinkEntry) wait_list;
enum {
NODE_STATUS_NEW = 0,
NODE_STATUS_INFLIGHT = 1,
@@ -94,6 +100,7 @@ typedef struct PCacheAIOCBRead {
uint64_t offset;
uint64_t bytes;
QEMUIOVector *qiov;
+ int ref;
int ret;
} PCacheAIOCBRead;
@@ -147,18 +154,49 @@ static void read_cache_data(PCacheAIOCBRead *acb,
PCacheNode *node,
assert(copy == size);
}
+static void pcache_aio_read(PCacheAIOCBRead *acb, PCacheNode *node)
+{
+ ACBLinkEntry *link;
+
+ if (node->status == NODE_STATUS_COMPLETED) {
+ read_cache_data(acb, node, acb->offset, acb->bytes);
+ return;
+ }
+
+ assert(node->status == NODE_STATUS_INFLIGHT ||
+ node->status == NODE_STATUS_REMOVE);
+
+ link = g_malloc(sizeof(*link));
+ link->acb = acb;
+
+ QTAILQ_INSERT_HEAD(&node->wait_list, link, entry);
+ acb->ref++;
+}
+
+static void aio_read_complete(PCacheAIOCBRead *acb, int ret)
+{
+ if (ret < 0 && acb->ret == 0) {
+ acb->ret = ret;
+ }
+
+ assert(acb->ref > 0);
+ if (--acb->ref == 0) {
+ qemu_coroutine_enter(acb->co);
+ }
+}
+
static void pcache_aio_read_cb(void *opaque, int ret)
{
PCacheAIOCBRead *acb = opaque;
- acb->ret = ret;
- qemu_coroutine_enter(acb->co);
+ aio_read_complete(acb, ret);
}
static void pcache_aio_readahead_cb(void *opaque, int ret)
{
PCacheAIOCBReadahead *acb = opaque;
PCacheNode *node = acb->node;
+ ACBLinkEntry *link, *next;
assert(node->status == NODE_STATUS_INFLIGHT ||
node->status == NODE_STATUS_REMOVE);
@@ -171,6 +209,20 @@ static void pcache_aio_readahead_cb(void *opaque, int ret)
rbcache_remove(s->cache, &node->common);
}
}
+
+ QTAILQ_FOREACH_SAFE(link, &node->wait_list, entry, next) {
+ PCacheAIOCBRead *acb_read = link->acb;
+
+ QTAILQ_REMOVE(&node->wait_list, link, entry);
+ g_free(link);
+
+ if (ret == 0) {
+ read_cache_data(acb_read, node, acb_read->offset, acb_read->bytes);
+ }
+
+ aio_read_complete(acb_read, ret);
+ }
+
pcache_node_unref(node);
qemu_coroutine_enter(acb->co);
@@ -254,6 +306,7 @@ static RBCacheNode *pcache_node_alloc(uint64_t offset,
uint64_t bytes,
node->data = g_malloc(bytes);
node->status = NODE_STATUS_NEW;
node->ref = 1;
+ QTAILQ_INIT(&node->wait_list);
return &node->common;
}
@@ -379,7 +432,7 @@ static int pcache_lookup_data(PCacheAIOCBRead *acb)
BDRVPCacheState *s = acb->bs->opaque;
PCacheNode *node = rbcache_search(s->cache, acb->offset, acb->bytes);
- if (node == NULL || node->status != NODE_STATUS_COMPLETED) {
+ if (node == NULL) {
return CACHE_MISS;
}
@@ -387,7 +440,7 @@ static int pcache_lookup_data(PCacheAIOCBRead *acb)
if (node->common.offset <= acb->offset &&
node->common.offset + node->common.bytes >= acb->offset + acb->bytes)
{
- read_cache_data(acb, node, acb->offset, acb->bytes);
+ pcache_aio_read(acb, node);
return CACHE_HIT;
}
@@ -405,6 +458,7 @@ static coroutine_fn int pcache_co_preadv(BlockDriverState
*bs, uint64_t offset,
.offset = offset,
.bytes = bytes,
.qiov = qiov,
+ .ref = 1,
};
int status;
@@ -417,14 +471,17 @@ static coroutine_fn int pcache_co_preadv(BlockDriverState
*bs, uint64_t offset,
update_req_stats(s->req_stats, offset, bytes);
status = pcache_lookup_data(&acb);
- if (status == CACHE_HIT) {
- return 0;
+ if (status == CACHE_MISS || status == PARTIAL_CACHE_HIT) {
+ bdrv_aio_preadv(bs->file, offset, qiov, bytes,
+ pcache_aio_read_cb, &acb);
}
- bdrv_aio_preadv(bs->file, offset, qiov, bytes, pcache_aio_read_cb, &acb);
-
pcache_readahead_request(&acb);
+ if (status == CACHE_HIT && --acb.ref == 0) {
+ return 0;
+ }
+
out:
qemu_coroutine_yield();
--
2.10.1
- [Qemu-block] [PATCH v1 00/18] I/O prefetch cache, Pavel Butsykin, 2016/11/15
- [Qemu-block] [PATCH v1 14/18] backup/pcache: pick up parts of the cache, Pavel Butsykin, 2016/11/15
- [Qemu-block] [PATCH v1 08/18] block/pcache: updating statistics for overlapping requests, Pavel Butsykin, 2016/11/15
- [Qemu-block] [PATCH v1 12/18] block/pcache: add reading data from the cache, Pavel Butsykin, 2016/11/15
- [Qemu-block] [PATCH v1 03/18] util/rbtree: add rbtree from linux kernel, Pavel Butsykin, 2016/11/15
- [Qemu-block] [PATCH v1 06/18] block/pcache: statistics collection read requests, Pavel Butsykin, 2016/11/15