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author | Sergio Lopez <slp@redhat.com> | 2021-08-24 15:11:58 +0200 |
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committer | Dr. David Alan Gilbert <dgilbert@redhat.com> | 2021-09-16 14:50:48 +0100 |
commit | 046d91c83caac29e2ba26c63fd7d685a57463f6d (patch) | |
tree | 664fc5f3f4cf3f832f480e836bb467c4d9f884ab | |
parent | 8cfd339b3d402f913fe520a4f35f30152fb4fb80 (diff) | |
download | qemu-046d91c83caac29e2ba26c63fd7d685a57463f6d.zip qemu-046d91c83caac29e2ba26c63fd7d685a57463f6d.tar.gz qemu-046d91c83caac29e2ba26c63fd7d685a57463f6d.tar.bz2 |
virtiofsd: Reverse req_list before processing it
With the thread pool disabled, we add the requests in the queue to a
GList, processing by iterating over there afterwards.
For adding them, we're using "g_list_prepend()", which is more
efficient but causes the requests to be processed in reverse order,
breaking the read-ahead and request-merging optimizations in the host
for sequential operations.
According to the documentation, if you need to process the request
in-order, using "g_list_prepend()" and then reversing the list with
"g_list_reverse()" is more efficient than using "g_list_append()", so
let's do it that way.
Testing on a spinning disk (to boost the increase of read-ahead and
request-merging) shows a 4x improvement on sequential write fio test:
Test:
fio --directory=/mnt/virtio-fs --filename=fio-file1 --runtime=20
--iodepth=16 --size=4G --direct=1 --blocksize=4K --ioengine libaio
--rw write --name seqwrite-libaio
Without "g_list_reverse()":
...
Jobs: 1 (f=1): [W(1)][100.0%][w=22.4MiB/s][w=5735 IOPS][eta 00m:00s]
seqwrite-libaio: (groupid=0, jobs=1): err= 0: pid=710: Tue Aug 24 12:58:16 2021
write: IOPS=5709, BW=22.3MiB/s (23.4MB/s)(446MiB/20002msec); 0 zone resets
...
With "g_list_reverse()":
...
Jobs: 1 (f=1): [W(1)][100.0%][w=84.0MiB/s][w=21.5k IOPS][eta 00m:00s]
seqwrite-libaio: (groupid=0, jobs=1): err= 0: pid=716: Tue Aug 24 13:00:15 2021
write: IOPS=21.3k, BW=83.1MiB/s (87.2MB/s)(1663MiB/20001msec); 0 zone resets
...
Signed-off-by: Sergio Lopez <slp@redhat.com>
Message-Id: <20210824131158.39970-1-slp@redhat.com>
Reviewed-by: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Dr. David Alan Gilbert <dgilbert@redhat.com>
-rw-r--r-- | tools/virtiofsd/fuse_virtio.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/tools/virtiofsd/fuse_virtio.c b/tools/virtiofsd/fuse_virtio.c index fc2564a..8f4fd16 100644 --- a/tools/virtiofsd/fuse_virtio.c +++ b/tools/virtiofsd/fuse_virtio.c @@ -716,6 +716,7 @@ static void *fv_queue_thread(void *opaque) /* Process all the requests. */ if (!se->thread_pool_size && req_list != NULL) { + req_list = g_list_reverse(req_list); g_list_foreach(req_list, fv_queue_worker, qi); g_list_free(req_list); req_list = NULL; |