Re: Performance problem with GC enabled
Re: Performance problem with GC enabled
- Subject: Re: Performance problem with GC enabled
- From: Bill Bumgarner <email@hidden>
- Date: Thu, 12 Mar 2009 08:39:23 -0700
On Mar 12, 2009, at 6:04 AM, John Engelhart wrote:
[.... way too many words deleted.... ... please try to succinctly
state issues in the future ....]
You have created a micro benchmark that demonstrates a significant bit
of overhead from GC vs. non-GC.
While micro benchmarks are certainly useful, they must be taken with a
grain of salt. Specifically, a real world app is not generally going
to go do, say, 10 bazillion of the operations in the micro benchmark
one after the other with zero feedback to the user. Typically, a
real world app would have progress bar(s), live button(s), and
displays that are updated.
GC was optimized for the real world situation. In Leopard, the GC
overhead is generally less than 10% CPU overhead and 10% memory
footprint overhead for the whole application. In some specific
measurements [of Xcode, for example, comparing GC vs. non-GC
performance], GC is actually significantly more efficient than non-
GC. In others, non-GC is still quite a bit more efficient. But,
overall and for the general user experience, GC on Leopard beats the
general 10%/10% mark.
And, just like every other component of Mac OS X, the goal is to make
the collector faster, more efficient, easier to use, and more powerful
with each successive release of Mac OS X.
This is where your micro benchmark (and others like it) comes in.
File a bug with your test case and attach the bits of software
necessary to reproduce it. Binaries are just fine. We will quite
likely add it to the growing test suite of tests if it is a micro
benchmark of something we aren't already tracking.
Also, keep in mind that a *ton* of time has passed since the Leopard
collector was released. The GC team has not been idle. If you have
access to Snow Leopard seeds, you should re-test on Snow Leopard.
b.bum
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