| re: MSE1::mse_chenis.mse.tay.dec.com::chenis
Ken,
I'm speaking entirely out of turn here, but my first impression is that
the "memory bottleneck" about which Microsoft writes is the inadequacy
of the AMOUNT of physical memory and not the speed of
processors/memory.
/Bill
|
| It depends how you are resolving them:
* 12 pages/second resolved in main memory would not hurt
* 12 pages/second resolved from disk with 1 io/sec wouldn't hurt much
- see perfmon/Add/Memory/Pages Input/sec and Pages Output/sec
* 12 pages/second resolved by doing 12 disk io/sec may start being
fairly noticeable!
- see perfmon/Add/Memory/Page Reads/sec and Pages Writes/sec
A (simple) view of this is that disks commonly spin 60 times/sec,
although more modern ones do 90/sec. But suppose you have 60. If your
workload to the disk is doing ANY seeking, you'll be lucky to sustain
30 i/o sec to a single drive. So if you have one drive that is being
used for paging (i.e. you haven't spread it over multiple spindles) and
if you're doing 12 i/o sec, that is substantial fraction of its
capacity. You might start feeling it.
Different question: does your system have other useful work to do
whilst page faults are resolved? Or are you running just the single
application? If so, then it'll be more noticeable.
On the other hand, suppose you're running a system with lots of
interesting work going on, and one process can pick up and run whilst
another one waits for paging IO. Suppose you've also spread the
pagefiles out over several spindles. In that case, 12 io/sec might not
be noticeable at all.
As .1 points out, this sort of memory bottleneck gets relieved when
you buy more memory. That's easier than buying a whole new 4100 with
*faster* memory.
/john henning
csd performance group
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