[PATCH] lib/oeqa/qemurunner: Use a timeout in select() call

[PATCH] lib/oeqa/qemurunner: Use a timeout in select() call

[Richard Purdie]

A 0 value to select.select() immediately returns with no timeout. This was
pegging the cpu at 100% for the python process which was bad and may be
contributing to some of the timeout problems.

Profile from -P of a core-image-minimal before:

    97526792 function calls (97525652 primitive calls) in 45.189 seconds

and after:

       50204 function calls (49064 primitive calls) in 17.318 seconds

Saving 97.5 million function calls has to be good :)

(From OE-Core rev: a572348c7ec1eb82fa2e5c977b27c24b4a9b29a1)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
---
diff --git a/meta/lib/oeqa/utils/qemurunner.py b/meta/lib/oeqa/utils/qemurunner.py
index e7bd8b1..f837800 100644
--- a/meta/lib/oeqa/utils/qemurunner.py
+++ b/meta/lib/oeqa/utils/qemurunner.py
@@ -101,7 +101,7 @@ class QemuRunner:
             reachedlogin = False
             stopread = False
             while time.time() < endtime and not stopread:
-                sread, swrite, serror = select.select(socklist, [], [], 0)
+                sread, swrite, serror = select.select(socklist, [], [], 0.1)
                 for sock in sread:
                     if sock is self.server_socket:
                         self.qemusock, addr = self.server_socket.accept()

Re: [PATCH] lib/oeqa/qemurunner: Use a timeout in select() call

[Burton, Ross]

On 6 September 2013 15:42, Richard Purdie
<richard.purdie@linuxfoundation.org> wrote:
> -                sread, swrite, serror = select.select(socklist, [], [], 0)
> +                sread, swrite, serror = select.select(socklist, [], [], 0.1)

As discussed on IM, for the purposes of this loop a timeout of seconds
instead of fractions of seconds would be more correct, although we're
obviously going to be having diminishing returns.

Ross

Re: [PATCH] lib/oeqa/qemurunner: Use a timeout in select() call

[Richard Purdie]

On Fri, 2013-09-06 at 15:46 +0100, Burton, Ross wrote:
> On 6 September 2013 15:42, Richard Purdie
> <richard.purdie@linuxfoundation.org> wrote:
> > -                sread, swrite, serror = select.select(socklist, [], [], 0)
> > +                sread, swrite, serror = select.select(socklist, [], [], 0.1)
> 
> As discussed on IM, for the purposes of this loop a timeout of seconds
> instead of fractions of seconds would be more correct, although we're
> obviously going to be having diminishing returns.

Basically, agreed. I've pushed this into master-next for testing
purposes whilst we discuss what this really should be. I think 5 might
be a good number. 

Cheers,

Richard

Re: [PATCH] lib/oeqa/qemurunner: Use a timeout in select() call

[Burton, Ross]

On 6 September 2013 15:50, Richard Purdie
<richard.purdie@linuxfoundation.org> wrote:
> Basically, agreed. I've pushed this into master-next for testing
> purposes whilst we discuss what this really should be. I think 5 might
> be a good number.

That certainly seems like a compromise between needless spinning and a
noticeable delta between requested and actual overall timeout.

Ross