[Virtio-fs] [PATCH v4 0/2] virtiofsd: Improve io bandwidth by replacing pwrite with pwritev

[piaojun]

On 2019/8/11 19:15, Eric Ren wrote:
> Hi,
> 
> On Sun, Aug 11, 2019 at 10:46:02AM +0800, piaojun wrote:
>>
>>
>> On 2019/8/11 10:06, Eric Ren wrote:
>>> Hi jun,
>>>
>>> On Fri, Aug 09, 2019 at 08:50:12AM +0800, piaojun wrote:
>>>> >From my test, write bandwidth will be improved greatly by replacing
>>>> pwrite with pwritev, and the test result as below:
>>>
>>> Could you share more information about this testing?
>>>
>>> - args for qemu: cache size?
>>> - args for virtiofsd: which cache mode？
>>> - DAX is used, right?
>>
>> DAX is disabled, as this optimization only works on Host side.
> 
> 
> OK, thanks for the info.
> 
> The test runs in KATA container, which use DAX as its default mount
> option.
> 
>>
>>>
>>> - which kind of disk are you using, what's then IOPS/BW limit?
>>>
>>> I tried this patch with HDD disk - IOPS:5000, BW: 140MB/s.
>>
>> I used EXT4 and ramdisk as backend device.
>>
>>>
>>> - VM: 4 vcpus, 8G mem
>>> - cache=always, cache-size=8G, DAX
>>> - fio job
>>>
>>> ```
>>> [global]
>>> fsync=0
>>> name=virtiofs-test
>>> filename=fio-test
>>> directory=$mntdir   # share dir for test sitting on the disk
>>> rw=randwrite
>>> bs=4K
>>
>> *bs* should be 1M for bandwidth test which makes writev works well.
> 
> Yes, but seq write "rw=write" is also good fr BW test, right?

Right.

Jun

> 
>>
>>> direct=1
>>> numjobs=1
>>> time_based=0
>>>
>>> [file1]
>>> size=2G
>>> io_size=40M
>>> ioengine=libaio
>>> iodepth=128
>>> ```
>>> - without this patch
>>>
>>> ```
>>> file1: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=128
>>> fio-3.1
>>> Starting 1 process
>>>
>>> file1: (groupid=0, jobs=1): err= 0: pid=11: Sat Aug 10 11:33:29 2019
>>>   write: IOPS=985, BW=3942KiB/s (4037kB/s)(40.0MiB/10390msec)
>>> ```
>>>
>>> - with this patch applied
>>>
>>> ```
>>> file1: (g=0): rw=randwrite, bs=(R) 4096B-4096B, (W) 4096B-4096B, (T) 4096B-4096B, ioengine=libaio, iodepth=128
>>> fio-3.1
>>> Starting 1 process
>>>
>>> file1: (groupid=0, jobs=1): err= 0: pid=10: Sat Aug 10 15:31:57 2019
>>>   write: IOPS=1056, BW=4224KiB/s (4326kB/s)(40.0MiB/9696msec)
>>>
>>> ```
>>>
>>> the number is even worse than 9pfs.
>>
>> Please modify your testcase as mentioned above, and share your result
>> again. I'm glad to find out where the problem is.
> 
> Will come back if I get the number.
> 
> Thanks,
> Eric
> 
>>
>> Jun
>>
>>>
>>> Thanks,
>>> Eric
>>>
>>>>
>>>> ---
>>>> pwrite:
>>>> # fio -direct=1 -time_based -iodepth=64 -rw=randwrite -ioengine=libaio -bs=1M -size=1G -numjob=16 -runtime=30 -group_reporting -name=file -filename=/mnt/virtiofs/file
>>>> file: (g=0): rw=randwrite, bs=1M-1M/1M-1M/1M-1M, ioengine=libaio, iodepth=64
>>>> ...
>>>> fio-2.13
>>>> Starting 16 processes
>>>> Jobs: 16 (f=16): [w(16)] [100.0% done] [0KB/886.0MB/0KB /s] [0/886/0 iops] [eta 00m:00s]
>>>> file: (groupid=0, jobs=16): err= 0: pid=5799: Tue Aug 6 18:48:26 2019
>>>> write: io=26881MB, bw=916988KB/s, iops=895, runt= 30018msec
>>>>
>>>> pwritev:
>>>> # fio -direct=1 -time_based -iodepth=64 -rw=randwrite -ioengine=libaio -bs=1M -size=1G -numjob=16 -runtime=30 -group_reporting -name=file -filename=/mnt/virtiofs/file
>>>> file: (g=0): rw=randwrite, bs=1M-1M/1M-1M/1M-1M, ioengine=libaio, iodepth=64
>>>> ...
>>>> fio-2.13
>>>> Starting 16 processes
>>>> Jobs: 16 (f=16): [w(16)] [100.0% done] [0KB/1793MB/0KB /s] [0/1793/0 iops] [eta 00m:00s]
>>>> file: (groupid=0, jobs=16): err= 0: pid=6328: Tue Aug 6 18:22:17 2019
>>>> write: io=52775MB, bw=1758.7MB/s, iops=1758, runt= 30009msec
>>>> ---
>>>>
>>>> This patch introduces writev and pwritev for lo_write_buf(). I tried my
>>>> best not doing harm to the origin code construct, and there will be
>>>> some *useless* branches in fuse_buf_copy_one() which are hard to judge
>>>> if they will be useful in the future. So I just leave them alone
>>>> safely. If the cleanup work is necessary, please let me know.
>>>>
>>>> v2
>>>>   - Split into two patches
>>>>   - Add the lost flags support, such as FUSE_BUF_PHYS_ADDR
>>>>
>>>> v3
>>>>   - use git send-email to make the patch set in one thread
>>>>   - move fuse_buf_writev() into fuse_buf_copy()
>>>>   - use writev for the src buffers when they're alread already mapped by the daemon process
>>>>   - use calloc to replace malloc
>>>>   - set res 0 if writev() returns 0
>>>>
>>>> v4
>>>>   - iterate from in_buf->buf[0] rather than buf[1]
>>>>   - optimize the code to make it more elegant
>>>>
>>>> Jun Piao (2):
>>>>   add definition of fuse_buf_writev().
>>>>   use fuse_buf_writev to replace fuse_buf_write for better performance
>>>>
>>>> Signed-off-by: Jun Piao <piaojun at huawei.com>
>>>> Suggested-by: Dr. David Alan Gilbert <dgilbert at redhat.com>
>>>> Suggested-by: Stefan Hajnoczi <stefanha at redhat.com>
>>>> ---
>>>>  buffer.c      |   48 ++++++++++++++++++++++++++++++++++++++++++++++++
>>>>  fuse_common.h |   14 ++++++++++++++
>>>>  seccomp.c     |    2 ++
>>>>  3 files changed, 64 insertions(+)
>>>> --
>>>>
>>>> _______________________________________________
>>>> Virtio-fs mailing list
>>>> Virtio-fs at redhat.com
>>>> https://www.redhat.com/mailman/listinfo/virtio-fs
>>> .
>>>
> .
>