Re: Performance and custom tags w/buffers=True

On Apr 7, 2006, at 10:28 AM, Jonathan Ellis wrote:

> On Thu, 6 Apr 2006 16:55:34 -0400, "Philip Semanchuk"
> <[email protected]> said:
>> Hi all,
>> I've been using Spyce in command line mode to generate reports. The
>> runtime suddenly ballooned and I tracked it down to a custom tag I had
>> written. Further experimentation showed that the tag behaved very
>> differently (performance-wise) depending on whether or not I set
>> buffers=True in the tag definition. I wrote a short page to illustrate
>> the problem:
>
>> Can anyone else (a) repeat these results and, better yet, (b) explain
>> what's going on?
>
> Well, the core buffer code is pretty much unchanged since 1.3, but
> compiling tags with buffering is relatively new.  Rimon was something
> of a performance nazi, so my guess is it's the compiled code's fault,
> rather than the execution model, but it may be worth testing that
> assumption.
>
> In any case, you can see the difference in the generated code, both
> for your page and the tag, by running spyceCompile from the command
> line.  (I don't think the page code will be any different, but
> I wouldn't place too much faith in my memory for that, either. :)

Thanks, Jonathan. I had a look at the generated code last night and the 
two versions differ, but not in any substantial way that I could see. I 
think the buffers=True version created the request, response, stdout 
and error objects in the body() function whereas the buffers=False 
version moved that code to the begin() function. It didn't seem to me 
that that would make any difference in performance.

This behavior isn't a big deal to me since custom tags are just a 
convenience and I can replace them with a bit of code, but the big 
performance hit seems like a trap for the unwary. At least now it is 
documented (sort of).

BTW I neglected to mention that I see this behavior on my 
FreeBSD/Python 2.4/x86 machine as well as under OS X/Python 2.3/PPC.

bye
Philip






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