[Qemu-devel] [Bug 1253563] [NEW] bad performance with rng-egd backend

[Qemu-devel] [Bug 1253563] [NEW] bad performance with rng-egd backend

[Amos Kong]

Public bug reported:


1. create listen socket
# cat /dev/random | nc -l localhost 1024

2. start vm with rng-egd backend

./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
-chardev socket,host=localhost,port=1024,id=chr0 \
-object rng-egd,chardev=chr0,id=rng0 \
-device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000

(guest) # dd if=/dev/hwrng of=/dev/null

note: cancelling dd process by Ctrl+c, it will return the read speed.

Problem:   the speed is around 1k/s

===================

If I use rng-random backend (filename=/dev/random), the speed is about
350k/s).

It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

I tried to change rng_egd_chr_can_read() always returns 1,  the speed is
improved to (about 400k/s)

Problem: we can't poll the content in time currently


Any thoughts?

Thanks, Amos

** Affects: qemu
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1253563

Title:
  bad performance with rng-egd backend

Status in QEMU:
  New

Bug description:
  
  1. create listen socket
  # cat /dev/random | nc -l localhost 1024

  2. start vm with rng-egd backend

  ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
  -chardev socket,host=localhost,port=1024,id=chr0 \
  -object rng-egd,chardev=chr0,id=rng0 \
  -device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000

  (guest) # dd if=/dev/hwrng of=/dev/null

  note: cancelling dd process by Ctrl+c, it will return the read speed.

  Problem:   the speed is around 1k/s

  ===================

  If I use rng-random backend (filename=/dev/random), the speed is about
  350k/s).

  It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
  The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

  I tried to change rng_egd_chr_can_read() always returns 1,  the speed
  is improved to (about 400k/s)

  Problem: we can't poll the content in time currently

  
  Any thoughts?

  Thanks, Amos

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[Qemu-devel] [Bug 1253563] [NEW] bad performance with rng-egd backend

[Launchpad Bug Tracker]

You have been subscribed to a public bug by Amos Kong (amoskong):


1. create listen socket
# cat /dev/random | nc -l localhost 1024

2. start vm with rng-egd backend

./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
-chardev socket,host=localhost,port=1024,id=chr0 \
-object rng-egd,chardev=chr0,id=rng0 \
-device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000

(guest) # dd if=/dev/hwrng of=/dev/null

note: cancelling dd process by Ctrl+c, it will return the read speed.

Problem:   the speed is around 1k/s

===================

If I use rng-random backend (filename=/dev/random), the speed is about
350k/s).

It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

I tried to change rng_egd_chr_can_read() always returns 1,  the speed is
improved to (about 400k/s)

Problem: we can't poll the content in time currently


Any thoughts?

Thanks, Amos

** Affects: qemu
     Importance: Undecided
         Status: New

-- 
bad performance with rng-egd backend
https://bugs.launchpad.net/bugs/1253563
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Re: [Qemu-devel] [Bug 1253563] [NEW] bad performance with rng-egd backend

[Amos Kong]

On Thu, Nov 21, 2013 at 09:24:11AM -0000, Amos Kong wrote:
> Public bug reported:
> 
> 
> 1. create listen socket
> # cat /dev/random | nc -l localhost 1024
> 
> 2. start vm with rng-egd backend
> 
> ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
> -chardev socket,host=localhost,port=1024,id=chr0 \
> -object rng-egd,chardev=chr0,id=rng0 \
> -device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000
> 
> (guest) # dd if=/dev/hwrng of=/dev/null
> 
> note: cancelling dd process by Ctrl+c, it will return the read speed.
> 
> Problem:   the speed is around 1k/s
> 
> ===================
> 
> If I use rng-random backend (filename=/dev/random), the speed is about
> 350k/s).
> 
> It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
> The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

Currently we have a request queue to cache un-processed request,
but new request_entropy is only comming when last request is processed
(chr dev data is filled to request->data, copied to VQ, and notify
virtio.

So the queue always has 0 or 1 items. The request process is designed
to sync, but it doesn't work.

Does this limitation come from virtio-rng driver in guest? 
 
> I tried to change rng_egd_chr_can_read() always returns 1,  the speed is
> improved to (about 400k/s)
> 
> Problem: we can't poll the content in time currently
 
 
> Any thoughts?
> 
> Thanks, Amos

[Bug 1253563] Re: bad performance with rng-egd backend

[Thomas Huth]

Looking through old bug tickets... is this still an issue with the
latest version of QEMU? Or could we close this ticket nowadays?


** Changed in: qemu
       Status: New => Incomplete

-- 
You received this bug notification because you are a member of qemu-
devel-ml, which is subscribed to the bug report.
https://bugs.launchpad.net/bugs/1253563

Title:
  bad performance with rng-egd backend

Status in QEMU:
  Incomplete

Bug description:
  
  1. create listen socket
  # cat /dev/random | nc -l localhost 1024

  2. start vm with rng-egd backend

  ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
  -chardev socket,host=localhost,port=1024,id=chr0 \
  -object rng-egd,chardev=chr0,id=rng0 \
  -device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000

  (guest) # dd if=/dev/hwrng of=/dev/null

  note: cancelling dd process by Ctrl+c, it will return the read speed.

  Problem:   the speed is around 1k/s

  ===================

  If I use rng-random backend (filename=/dev/random), the speed is about
  350k/s).

  It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
  The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

  I tried to change rng_egd_chr_can_read() always returns 1,  the speed
  is improved to (about 400k/s)

  Problem: we can't poll the content in time currently

  
  Any thoughts?

  Thanks, Amos

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[Bug 1253563] Re: bad performance with rng-egd backend

[Amos Jianjun Kong]

Let's close this bug, it's passed 6 years.

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Title:
  bad performance with rng-egd backend

Status in QEMU:
  Incomplete

Bug description:
  
  1. create listen socket
  # cat /dev/random | nc -l localhost 1024

  2. start vm with rng-egd backend

  ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
  -chardev socket,host=localhost,port=1024,id=chr0 \
  -object rng-egd,chardev=chr0,id=rng0 \
  -device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000

  (guest) # dd if=/dev/hwrng of=/dev/null

  note: cancelling dd process by Ctrl+c, it will return the read speed.

  Problem:   the speed is around 1k/s

  ===================

  If I use rng-random backend (filename=/dev/random), the speed is about
  350k/s).

  It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
  The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

  I tried to change rng_egd_chr_can_read() always returns 1,  the speed
  is improved to (about 400k/s)

  Problem: we can't poll the content in time currently

  
  Any thoughts?

  Thanks, Amos

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[Bug 1253563] Re: bad performance with rng-egd backend

[Launchpad Bug Tracker]

[Expired for QEMU because there has been no activity for 60 days.]

** Changed in: qemu
       Status: Incomplete => Expired

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Title:
  bad performance with rng-egd backend

Status in QEMU:
  Expired

Bug description:
  
  1. create listen socket
  # cat /dev/random | nc -l localhost 1024

  2. start vm with rng-egd backend

  ./x86_64-softmmu/qemu-system-x86_64 --enable-kvm -mon chardev=qmp,mode=control,pretty=on -chardev socket,id=qmp,host=localhost,port=1234,server,nowait -m 2000 -device virtio-net-pci,netdev=h1,id=vnet0 -netdev tap,id=h1 -vnc :0 -drive file=/images/RHEL-64-virtio.qcow2 \
  -chardev socket,host=localhost,port=1024,id=chr0 \
  -object rng-egd,chardev=chr0,id=rng0 \
  -device virtio-rng-pci,rng=rng0,max-bytes=1024000,period=1000

  (guest) # dd if=/dev/hwrng of=/dev/null

  note: cancelling dd process by Ctrl+c, it will return the read speed.

  Problem:   the speed is around 1k/s

  ===================

  If I use rng-random backend (filename=/dev/random), the speed is about
  350k/s).

  It seems that when the request entry is added to the list, we don't read the data from queue list immediately.
  The chr_read() is delayed, the virtio_notify() is delayed.  the next request will also be delayed. It effects the speed.

  I tried to change rng_egd_chr_can_read() always returns 1,  the speed
  is improved to (about 400k/s)

  Problem: we can't poll the content in time currently

  
  Any thoughts?

  Thanks, Amos

To manage notifications about this bug go to:
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