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Re: [Qemu-devel] [PATCH v2 0/7] curl: locking cleanups/fixes, coroutine

From: Richard W.M. Jones
Subject: Re: [Qemu-devel] [PATCH v2 0/7] curl: locking cleanups/fixes, coroutine conversion, remove aio_poll
Date: Wed, 10 May 2017 16:57:00 +0100
User-agent: Mutt/1.5.20 (2009-12-10)

On Wed, May 10, 2017 at 04:31:58PM +0200, Paolo Bonzini wrote:
> Since the last patch in v1 didn't work, I bit the bullet and converted
> the whole thing to coroutines (patches 4-6).  This in turns allows a more
> elegant solution to wait for CURLStates to get free (patch 7).
> I tested this by lowering CURL_NUM_STATES to 2.  With this change, the
> buggy case triggers a couple times while booting a Fedora netinst image.

This series fixes the original bug, so:

  Tested-by: Richard W.M. Jones <address@hidden>

I think the Reported-by in patch 3 should credit Kun Wei for finding
the bug, and we should probably mention the BZ too:

  Reported-by: Kun Wei <address@hidden>
  Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1447590

A nit pick perhaps but in patch 5 you say "This was broken before for
disks > 2TB, but now it would break at 4GB.".
I understand after reading it a few times that you mean it would be
broken at 4GB, if you hadn't changed size_t -> uint64_t (on 32 bit
platforms).  Perhaps better to clarify that sentence.


I also ran some performance and stability testing.  I used virt-ls for
this.  The following command will iterate over every file in a remote
guest image and print an md5sum:

  LIBGUESTFS_HV=~/d/qemu/x86_64-softmmu/qemu-system-x86_64 \
  virt-ls -a http://somehost/rhel-guest-image-7.1-20150224.0.x86_64.qcow2 \
          -lR --checksum /

I timed this with and without your patches, but there was no
significant difference (but note that virt-ls is a fundamentally
sequential program).

It didn't crash or hang at any time during my testing.


Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
virt-p2v converts physical machines to virtual machines.  Boot with a
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