"Dirk" == Dirk Vleugels <[EMAIL PROTECTED]> writes:
Dirk> Hi,
>> As an experiment you could try running one or more of
>> your Perl scripts with
>> ppgsz -o heap=8K /path/to/script
>> ormance problem disappears. If this performs
>> better, then your problem is very likely what I've
>> described. If the
>> performance problems persist in this case, then the
>> problem may be
>> something else.
Dirk> This fixes it!
Dirk> No more high smtx values (even when launching hundreds of perl
Dirk> scripts) with this page size, and the box stays responsive.
Dirk> So i assume the box is running low on main memory even though
Dirk> vmstat scan rate is low?
The VM system is programmed to try to use large pages as quickly as
possible on a T2000, due to small TLBs. There's a trade off here
between TLB misses and the ability to get large pages. So ppgsz -o
heap=8K tells the VM system to not try to get large pages and just use
8K pages for a particular application. The tradeoff is that it's
likely you'll see more TLB misses, but it appears that performs better
than the other way (it appears to do so).
You might also try a compromise position of
ppgsz -o heap=64K /path/to/script
This will cause the application to use 64K pages, which it still will
have to find, but it should be more able to do that than 4M pages.
Dirk> Is there any other fix than migrating some memory hungry processes?
I don't know. You could ask the Sun support folks if there have been
any fixes to this area that might help.
Dirk> Could i run more processes with this default heap page size? Is
Dirk> this recommended or a bad idea (i guess they will brk what they
Dirk> need anyways). Something to put into /etc/system?
IF you want to try setting up a set of applications this way, you may
also want to investigate mpss.so.1. See the man page mpss.so.1(1).
This involves a preload and environment variables, so it has its
issues too.
I don't think there are any documented interfaces to turn off the
large page "out of box" behavior via /etc/system, and I'm not sure
you'd want to do that in general. Probably better to see if there are
patches for this problem or migrate some of your workload to other
servers.
Dirk> Thanx for your help!
You're welcome. I hope you come up with something that works for you
without too much pain.
--
Dave Marquardt
Sun Microsystems, Inc.
Austin, TX
+1 512 401-1077 (SUN internal: x64077)
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