Change log v3 -> v4:
1. Develop these into the non-RFC patches.
2. Fix some comments.
3. do declarations first.
Change log v2 -> v3:
1. Remove the unnecessary code for the bdrv_next_node().
2. Remove the change of the locking rules.
Even if this change can improve the performance, but it may
effect the consistency.
The Qemu uses the qmp_query_blockstats() function to get the
blockstats. As the function has been changed several times, it
becomes more complex and longer.
For the multi-disks guest, if we want to execute I/O operations
and this function at the same time. we can use the dataplane
feature to hold I/O performance does not drop. But, Normally
without this feature, How to reduce the decline in performance?
These patches refactor the qmp_query_blockstats() to make the
code easier to follow, and shorter as follows:
From:
+--------------+ +---------------------+
| 1 | | 4. |
|next_query_bds| |bdrv_query_bds_stats +---+
| | | | |
+--------^-----+ +-------------^-------+ |
| | |
+---------+----------+ +--------+-------+ |
| 0. | | 2. | |
|qmp_query_blockstats+------>bdrv_query_stats<----
| | | |
+--------------------+ +--------+-------+
|
+-------------v-------+
| 3. |
|bdrv_query_blk_stats |
| |
+---------------------+
To:
+--------------+
| |
+--------v-----------+ |
+---> 3. | |
+-------------------+ | |bdrv_query_bds_stats+--+
| 1. +--+ | |
| + +--------------------+
|qmp_query_blockstats--+
| | |
+-------------------+ | +--------------------+
| | 2. |
+---> |
|bdrv_query_blk_stats|
| |
+--------------------+
They also optimize the fuction by reducing its running time.
1. The function running time
the time it takes(ns) in each requests:
the disk numbers | 10 | 500
-------------------------------------
before these patches | 19429 | 667722
after these patches | 18536 | 627945
2. For the performance
used the dd command likes this to test:
dd if=date_1.dat of=date_2.dat conv=fsync oflag=direct bs=1k count=100k.
the I/O performance is degraded(%) during the monitor:
the disk numbers | 10 | 500
-------------------------------------
before these patches | 1.3 | 14.2
after these patches | 1.0 | 11.3
Dou Liyang (2):
block/qapi: reduce the coupling between the bdrv_query_stats and
bdrv_query_bds_stats
block/qapi: reduce the execution time of qmp_query_blockstats
block/qapi.c | 95 ++++++++++++++++++++++++++----------------------------------
1 file changed, 41 insertions(+), 54 deletions(-)