Re: Increase WinXP/jre CPU usage?
Steve Brecher wrote:
Patricia Shanahan <pats@acm.org> wrote:
Chris Uppal wrote:
in an article not as yet presented by my news server :( hence quoted
indirectly...
[...]
But don't assume that making the application use the other "cpu" will
necessarily speed anything up. HT is (for most purposes) better
regarded as a cheap marketing gimmick than a valid technology.
OK. Actually, I am using my P4 system only for development. The real
target is some hardware yet to be acquired which will undoubtedly be
dual-core. The current project is a self-tutorial; it's my first Java and
Eclipse IDE experience; it's a port from C.
In that case, you should probably use the opportunity to practice
parallelizing the job, so that you know how to take advantage of a
dual-core processor.
Or -- to put it another way -- the CPU usage reported by TaskManager
is misleading. It suggests that 50% of your available horse-power is
unused. My bet would be that it's more like 5% -- if not actually
zero.
I'm curious about why that would be, but as implied above it's rather idle
curiosity.
[now quoting Patricia]
Here's a suggestion for a cheap test:
1. Add, if the application does not already contain it, some
performance statistics collection keeping track of how much elapsed
time it takes to do a given quantity of the compute intensive work.
2. Run one copy of the application. Record the statistics.
Already done.
3. Run two copies of the application, simultaneously. Record the
statistics.
How important is (almost) exact simultaneity? Would starting one manually
via console, then another be sufficient? This would mean a delay of several
seconds; the run time is 3+ minutes. If not, it would be reasonably easy to
multi-thread the code if the the total workload didn't have to be
apportioned among the threads.
I would think that would be close enough. We are trying to tell the
difference between a throughput change that would justify programming
effort and a few percentage point change.
If it is likely to benefit from multi-threading, the total work rate
will be significantly higher with two copies than with one. If it is
the sort of case Chris is talking about, each copy will run at
slightly better than half the speed of the single copy.
This test automatically takes into account questions such as how much
time a thread of your application spends waiting for memory, which can
affect how much you gain from hyperthreading.
Would there be reasons other than data caching that each copy would run at
better than half the speed of a single copy?
Very few jobs really use ALL the cycles when they are "running" on a
processor, so giving a hyperthreaded processor a second job should
produce some increase in total throughput.
Patricia