[Qemu-devel] [PATCH v1 15/18] block/pcache: drop used pcache nodes

[Pavel Butsykin <pbutsykin@virtuozzo.com>]

The pcache is directed to certain situations to sequential reads. This concept
allows to drop parts of the cache that were already used, which will reduce
the size of cache and the number of displaced nodes.

Signed-off-by: Pavel Butsykin <pbutsykin@virtuozzo.com>
---
 block/pcache.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/block/pcache.c b/block/pcache.c
index 40fa3f3..df4834a 100644
--- a/block/pcache.c
+++ b/block/pcache.c
@@ -83,6 +83,7 @@ typedef struct PCacheNode {
         NODE_STATUS_REMOVE    = 3,
         NODE_STATUS_DELETED   = 4, /* only for debugging */
     } status;
+    uint64_t rdcnt;
     int ref;
 } PCacheNode;
 
@@ -142,10 +143,14 @@ static uint64_t ranges_overlap_size(uint64_t offset1, uint64_t size1,
 static void read_cache_data(PCacheAIOCBRead *acb, PCacheNode *node,
                             uint64_t offset, uint64_t bytes)
 {
+    BDRVPCacheState *s = acb->bs->opaque;
     uint64_t qiov_offs = 0, node_offs = 0;
     uint64_t size;
     uint64_t copy;
 
+    assert(node->status == NODE_STATUS_COMPLETED ||
+           node->status == NODE_STATUS_REMOVE);
+
     if (offset < node->common.offset) {
         qiov_offs = node->common.offset - offset;
     } else {
@@ -156,6 +161,12 @@ static void read_cache_data(PCacheAIOCBRead *acb, PCacheNode *node,
 
     copy = qemu_iovec_from_buf(acb->qiov, qiov_offs,
                                node->data + node_offs, size);
+    node->rdcnt += size;
+    if (node->rdcnt >= node->common.bytes &&
+        node->status == NODE_STATUS_COMPLETED)
+    {
+        rbcache_remove(s->cache, &node->common);
+    }
     assert(copy == size);
 }
 
@@ -314,6 +325,7 @@ static RBCacheNode *pcache_node_alloc(uint64_t offset, uint64_t bytes,
 
     node->data = g_malloc(bytes);
     node->status = NODE_STATUS_NEW;
+    node->rdcnt = 0;
     node->ref = 1;
     QTAILQ_INIT(&node->wait_list);
 
-- 
2.10.1