From: Andi Kleen <ak@suse.de>
Date: Mon, 2 Dec 2002 10:07:56 +0100
> BTW, I bet your dynamic relocation tables are a bit larger too.
Somewhat, but does it matter? They are not kept in memory anyways.
It's all about how much data a ld.so relocation has to touch. But
preloading will help out here, even though that isn't in wide spread
use just yet.
And I was talking about user stack usage, not the kernel kind
:-)
Andi, do something very simple like run -m32 vs -m64 microbenchmarks,
I bet -m32 beats -m64 in all the lmbench lat_proc tests. On sparc64
it's (on a 2-way SMP system):
-m32 fork+exit: 360.8328 microseconds
-m32 fork+execve: 1342.2213 microseconds
-m32 fork+/bin/sh: 5497.0149 microseconds
-m64 fork+exit: 553.9076 microseconds
-m64 fork+execve: 1904.6315 microseconds
-m64 fork+/bin/sh: 6268.6932 microseconds
NOTE: make sure you change /bin/sh to be 32-bit/64-bit as
appropriate in the tests above.
So what is this on x86_64? :-) I think lat_proc is great becuase it
shows pure libc overhead in continually relocating the exit()
etc. symbols in the child for fork+exit, for example.
The reason I'm making such a stink about this is that I don't want
people believing that "the code generation improvements due to the
extra x86_64 registers available nullifies the bloat cost from
going to 64-bit"
To me, believe that is an utterly bogus claim and completely
misleading.
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This archive was generated by hypermail 2b29 : Sat Dec 07 2002 - 22:00:12 EST