Re: [Qemu-devel] [PATCH 4/6] tests: Add migration xbzrle test

[Juan Quintela <quintela@redhat.com>]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
>> Signed-off-by: Juan Quintela <quintela@redhat.com>

> +static void test_xbzrle(const char *uri)
>> +{
>> +    QTestState *from, *to;
>> +
>> +    test_migrate_start(&from, &to, uri);
>> +
>> +    /* We want to pick a speed slow enough that the test completes
>> +     * quickly, but that it doesn't complete precopy even on a slow
>> +     * machine, so also set the downtime.
>> +     */
>> +    /* 100 ms */
>> +    migrate_set_parameter(from, "downtime-limit", "100");
>> +    /* 1MB/s slow*/
>> +    migrate_set_parameter(from, "max-bandwidth", "100000000");
>> +
>> +    migrate_set_cache_size(from, "50000000");
>
> Why 50MB?  I guess this is an interesting test; the program
> dirties 100MB of RAM repeatedly, one byte/page.  So 50MB is probably
> not much use becuase it'll thrash.

No good reason.
What I want (tm):
- if you have fast hardware, test is as fast as it can
- if you don't have fast hardware (or very overloaded), it don't fail

My current idea is:
- using 1GB/s for speed
- using downtime = 1ms when I want to wait for migration not converge
- using downtime = 300ms when I want it to finish

I am open to other numbers.

>> +    migrate_set_capability(from, "xbzrle", "true");
>> +    migrate_set_capability(to, "xbzrle", "true");
>> +    /* Wait for the first serial output from the source */
>> +    wait_for_serial("src_serial");
>> +
>> +    migrate(from, uri);
>> +
>> +    wait_for_migration_pass(from);
>> +
>> +    /* 1GB/s now it should converge */
>> +    migrate_set_parameter(from, "max-bandwidth", "1000000000");
>
> I wonder about doing a set_cache_size 150MB here, with a delay before
> the max-bandwidht?  If we're lucky at 150MB it'll start actually using
> the XBZRLE compression.
>
>> +    if (!got_stop) {
>> +        qtest_qmp_eventwait(from, "STOP");
>> +    }
>> +    qtest_qmp_eventwait(to, "RESUME");
>> +
>> +    wait_for_serial("dest_serial");
>> +    wait_for_migration_complete(from);
>> +
>> +    test_migrate_end(from, to);
>
> Extract xbzrle stats?

Thinking about that.

I actually would want to test that when I set something, read it back
that it is what I setted.  I gues I would use a similar trick to what
you do to get the pass number.

Later, Juan.