Dual-core & Parallel Compile Issues 2005-12-06 - By Brian Long
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Hello folks,
I'm grasping at straws here hoping someone else has run into issues
running dual-core Opterons (Sun V40z specifically). When we run a large
parallel compile with various j values (i.e. -j8, -j16, -j24, -j32,
-j40), we are able to compile the end product in much less time on a
quad single-core V40z (quad Opteron 852 / 2.6GHz) than on a quad
dual-core V40z (quad Opteron 875 / 2.2GHz). For example, with -j20, 7.4
mins vs. 9.6 mins without ClearCase and 13.7 mins. vs. 18.6 mins with
ClearCase). We have tried on the U5 and U6 kernel with zero improvement
seen between the two.
When compiling with large -j values on the dual-core system, the CPUs
stay 80% idle the majority of the time (as measured by sar on 10-sec
interval). On the single-core system, the CPU is much more utilized
throughout the build. I can provide graphs if anyone is interested. We
have not yet tried to duplicate the issue on RHEL 4 U2, but plan to try
in the next few days.
I would appreciate any pointers on how we might further investigate what
is causing the bottleneck. Are there known issues with the RHEL 3
kernel scheduler or anything else I should be aware of? Thanks.
/Brian/
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Brian Long | | |
IT Data Center Systems | .|||. .|||.
Cisco Linux Developer | ..:|||||||:...:|||||||:..
Phone: (919) 392-7363 | C i s c o S y s t e m s
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