Re: [External] Re: [PATCH 5/5] migration: Add integration test for 'qatzip' compression method

[Peter Xu]

On Wed, Feb 28, 2024 at 06:55:37PM -0800, Bryan Zhang . wrote:
> We can enable software fallback in the live migration path, which will also
> enable using software to run the QATzip tests (and will conveniently allow
> us to remove the awkward `qzInit` check in the test code). It also might be
> a good idea since it would also avoid failure in case of, e.g., a transient
> hardware problem?
> 
> Performance: The software fallback seems prohibitively slow. QATzip
> fallback uses the built-in zlib implementation, but I ran a migration test
> that normally takes zlib about 150 seconds and the QATzip fallback took
> about 30 minutes before my SSH session disconnected :P

When preparing the qatzip documentataion file, please mention this.  This
is definitely not expected by myself, we should suggest mostly never use
qatzip compatible (software) mode unless the admin is sure to have the
hardware support.

It should then only be used in qtest to cover the qatzip paths only.

> 
> Also, a note: When enabling software fallback, QATzip and the QAT driver
> will both repeatedly print a complaint to the QEMU monitor when trying to
> compress without hardware. Is it bad form to introduce
> seemingly-unsuppressable prints from dependencies, or is this acceptable?

It is definitely bad to keep printing the same message, no matter from
where.

Why it repeatedly do so?  Do you know why the library cannot make it
print_once()?

-- 
Peter Xu