On 12/01/2004 00:39 Oliver Jowett wrote:
> Paul Thomas wrote:
>> Having followed this very interesting thread, I'm still wondering
>> exactly how much measurable improvement could be achieved. I read an
>> article on IBM developerWorks (sorry can't remember the URL) which
>> stated that, on modern VMs, things like object creation aren't the
>> performance bogeys that they once were. So I'm thinking that before we
>> make a decision about committing to a change which might break someones
>> app, is there any way by which we could measure the effects of the
>> proposed change?
>
> The problem is that it's very specific to the application workload; what
> case do we measure?
I think you would need something which closely models you app's work load.
> The reason I'm interested in doing this for is not the direct CPU
> overhead of object creation (none of the JDBC code is on our main
> execution path), but the effect that object creation has on GC interval
> and pause. We're running a low-latency app where an extra 50ms pause due
> to GC has a large impact on our latency figures .. so the less garbage
> we generate in the first place, the better. We could farm the JDBC work
> out to a separate VM, but that gets complex quite fast.
Reducing the amount of garbage created is never a bad thing. Do you have
an estimate of the % reduction you think you could achieve?
>
> Aside from the change in behaviour, the change I'm proposing has no real
> downside I can see -- it's not a CPU-vs-memory tradeoff, we're just
> generating fewer intermediate copies altogether. More of a code
> complexity-vs-runtime cost tradeoff I suppose.
Sounds fine to me.
--
Paul Thomas
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