Greg Ames wrote:
>
> "Paul J. Reder" wrote:
> >
> >
> > These two functions could easily be merged,
>
> OK, that sounds like a good first step. But better still would be to
> make this so simple for the mainline code that no function or macro is
> called for. Just test one variable.
....
> I'm suggesting that the question, "Should I keep working?" is very
> simple conceptually, so the code to perform the test in the main loop
> should be dead simple. We can use your new field in the worker's slot
> of the scoreboard as the one and only place that needs to be checked to
> answer such a question. If we do that, there's no need for function
> calls or macros, which makes things simpler still. Yes, we would have
> to make the code that initiates graceful restart a tiny bit more
> complex, but I think that's a fair tradeoff. The generation numbers can
> remain separate, but unused for this purpose.
>
> Without your patch, we are touching 4 separate variables (deferred_die,
> ap_my_generation, ap_scoreboard_image, and
> ap_scoreboard_image->global.running_generation ) to answer "Should I
> keep working?". Worse case, that's 4 data cache lines that must be
> either already present in the cache or fetched, at two different spots
> in the request loop separated by what could be a long time delay. That
> seems like a lot, so I am advocating making the situation better by
> reducing rather than increasing the number of variables accessed.
I agree. When I wrote the initial version I was trying to maintain the
current separation of concepts, but felt it made for excessive code path.
I have rewritten the code to check for just one variable. I am currently
working to move the code to set the idle_die flag to the server during
restart to eliminate this code in the worker.
--
Paul J. Reder
-----------------------------------------------------------
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