[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize th
From: |
Stefan Hajnoczi |
Subject: |
Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats() |
Date: |
Wed, 21 Dec 2016 11:06:57 +0000 |
User-agent: |
Mutt/1.7.1 (2016-10-04) |
On Wed, Dec 21, 2016 at 05:13:39PM +0800, Dou Liyang wrote:
> Hi Stefan,
>
> At 12/20/2016 05:39 PM, Stefan Hajnoczi wrote:
> > On Tue, Dec 20, 2016 at 12:32:40AM +0800, Fam Zheng wrote:
> > > On Mon, 12/19 15:02, Stefan Hajnoczi wrote:
> > > > On Mon, Dec 19, 2016 at 04:51:22PM +0800, Dou Liyang wrote:
> > > > > These patches aim to refactor the qmp_query_blockstats() and
> > > > > improve the performance by reducing the running time of it.
> > > > >
> > > > > qmp_query_blockstats() is used to monitor the blockstats, it
> > > > > querys all the graph_bdrv_states or monitor_block_backends.
> > > > >
> > > > > There are the two jobs:
> > > > >
> > > > > 1 For the performance:
> > > > >
> > > > > 1.1 the time it takes(ns) in each time:
> > > > > the disk numbers | 10 | 500
> > > > > -------------------------------------
> > > > > before these patches | 19429 | 667722
> > > > > after these patches | 17516 | 557044
> > > > >
> > > > > 1.2 the I/O performance is degraded(%) during the monitor:
> > > > >
> > > > > the disk numbers | 10 | 500
> > > > > -------------------------------------
> > > > > before these patches | 1.3 | 14.2
> > > > > after these patches | 0.8 | 9.1
> > > >
> > > > Do you know what is consuming the remaining 9.1%?
> > > >
> > > > I'm surprised to see such a high performance impact caused by a QMP
> > > > command.
> > >
> > > If it's "performance is 9.1% worse only during the 557044 ns when the QMP
> > > command is being processed", it's probably becaues the main loop is
> > > stalled a
> > > bit, and it's not a big problem. I'd be very surprised if the degradation
> > > is
> > > more longer than that.
> >
> > It would be interesting to compare against virtio-blk dataplane. That
> > way the QMP command can execute without interfering with disk I/O activity.
> >
> > qemu-system-x86_64 ... \
> > -object iothread,id=iothread0 \
> > -drive if=none,id=drive0,file=vm.img,format=raw,aio=native,cache=none \
> > -device virtio-blk-pci,drive=drive0,iothread=iothread0
>
> Here is the result in the guest with 500 disks:
>
> QMP command | not execute | execute in each 0.5s |
> -------------------------------------------------------
> Average Times/s | 102.34675 | 103.128 |
>
> the degradation is 0.76%, that can be ignored.
>
> the dd command:
> dd if=date_1.dat of=date_2.dat conv=fsync oflag=direct bs=1k count=400k
Excellent. It's good to know that dataplane is a solution to this
problem.
Stefan
signature.asc
Description: PGP signature
- Re: [Qemu-devel] [PATCH RFC v2 1/4] block: refactor bdrv_next_node for readability, (continued)
- [Qemu-devel] [PATCH RFC v2 4/4] block/qapi: optimize the query function of the blockstats, Dou Liyang, 2016/12/19
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Stefan Hajnoczi, 2016/12/19
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Fam Zheng, 2016/12/19
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Stefan Hajnoczi, 2016/12/20
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Dou Liyang, 2016/12/20
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Stefan Hajnoczi, 2016/12/20
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Dou Liyang, 2016/12/20
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Stefan Hajnoczi, 2016/12/20
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Dou Liyang, 2016/12/21
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(),
Stefan Hajnoczi <=
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Dou Liyang, 2016/12/22
- Re: [Qemu-devel] [PATCH RFC v2 0/4] block/qapi: refactor and optimize the qmp_query_blockstats(), Dou Liyang, 2016/12/20