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[Qemu-devel] [PATCH v2 07/18] block/pcache: updating statistics for over
From: |
Pavel Butsykin |
Subject: |
[Qemu-devel] [PATCH v2 07/18] block/pcache: updating statistics for overlapping requests |
Date: |
Fri, 30 Dec 2016 17:31:31 +0300 |
When updating the statistics sometimes i/O requests can overlap each other,
in this case the requests are not stored in the statistics. It's not very good,
especially when the requests have a small range of intersection.
We can cut the requests in the intersection and add the pieces of requests in
the statistics. Maybe not significantly, but it can make the statistics more
accurate. Here, update_req_stats() adds the ability to save overlapping
requests.
Signed-off-by: Pavel Butsykin <address@hidden>
---
block/pcache.c | 36 +++++++++++++++++++++++++++++++++++-
1 file changed, 35 insertions(+), 1 deletion(-)
diff --git a/block/pcache.c b/block/pcache.c
index 1f3200af63..deac57c58d 100644
--- a/block/pcache.c
+++ b/block/pcache.c
@@ -46,6 +46,40 @@ typedef struct BDRVPCacheState {
uint64_t max_aio_size;
} BDRVPCacheState;
+static void update_req_stats(RBCache *rbcache, uint64_t offset, uint64_t bytes)
+{
+ do {
+ RBCacheNode *node = rbcache_search_and_insert(rbcache, offset, bytes);
+ /* The node was successfully added or already exists */
+ if (node->offset <= offset &&
+ node->offset + node->bytes >= offset + bytes)
+ {
+ break;
+ }
+
+ /* Request covers the whole node */
+ if (offset <= node->offset &&
+ offset + bytes >= node->offset + node->bytes)
+ {
+ rbcache_remove(rbcache, node);
+ continue;
+ }
+
+ if (offset < node->offset) {
+ RBCacheNode *new_node =
+ rbcache_node_alloc(rbcache, offset, node->offset - offset);
+ if (new_node != rbcache_insert(rbcache, new_node)) {
+ /* The presence of the node in this range is impossible */
+ abort();
+ }
+ break;
+ }
+
+ bytes = (offset + bytes) - (node->offset + node->bytes);
+ offset = node->offset + node->bytes;
+ } while (true);
+}
+
static coroutine_fn int pcache_co_preadv(BlockDriverState *bs, uint64_t offset,
uint64_t bytes, QEMUIOVector *qiov,
int flags)
@@ -53,7 +87,7 @@ static coroutine_fn int pcache_co_preadv(BlockDriverState
*bs, uint64_t offset,
BDRVPCacheState *s = bs->opaque;
if (s->max_aio_size >= bytes) {
- rbcache_search_and_insert(s->req_stats, offset, bytes);
+ update_req_stats(s->req_stats, offset, bytes);
}
return bdrv_co_preadv(bs->file, offset, bytes, qiov, flags);
--
2.11.0
- [Qemu-devel] [PATCH v2 00/18] I/O prefetch cache, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 11/18] block/pcache: add reading data from the cache, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 16/18] block/pcache: drop used pcache nodes, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 12/18] block/pcache: inflight readahead request waiting for read, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 02/18] util/rbtree: add rbtree from linux kernel, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 18/18] block/pcache: add tracepoints, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 15/18] block/pcache: pick up parts of the cache, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 03/18] util/rbcache: range-based cache core, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 07/18] block/pcache: updating statistics for overlapping requests,
Pavel Butsykin <=
- [Qemu-devel] [PATCH v2 14/18] block/pcache: up-to-date cache for removed nodes, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 08/18] block/pcache: add AIO readahead, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 17/18] qapi: allow blockdev-add for pcache, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 05/18] block/pcache: statistics collection read requests, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 10/18] block/pcache: cache invalidation on write requests, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 06/18] block/pcache: skip large aio read, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 04/18] tests/test-rbcache: add test cases, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 01/18] block/pcache: empty pcache driver filter, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 09/18] block/pcache: skip readahead for unallocated clusters, Pavel Butsykin, 2016/12/30
- [Qemu-devel] [PATCH v2 13/18] block/pcache: write through, Pavel Butsykin, 2016/12/30