Messages in this thread | | | Date | Wed, 06 Jul 2005 15:23:56 +0100 | From | Paulo Marques <> | Subject | Slowdown with randomize_va_space in 2.6.12.2 |
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Hi, all
I have a bash script that calls a small application several times (around 50 calls) that just send and receives data through an already open tcp socket to a local server through the loopback device. It also launches another small app several times that just reads a small file from disk and does some processing on it in memory.
We noticed a severe performance regression on this application under kernel 2.6.12.2 that we tracked down to the address space randomization patches:
# echo 0 > randomize_va_space # time ./script real 0m0.671s user 0m0.293s sys 0m0.325s
# echo 1 > randomize_va_space # time ./script real 0m3.310s user 0m2.712s sys 0m0.401s
Notice that the real time is 5x slower with "randomize_va_space" turned on. This is on a Transmeta Crusoe TM5600 at 533MHz.
What is weird is that most of the extra time is being accounted as user-space time, but the user-space application is exactly the same in both runs, only the "randomize_va_space" parameter changed.
I browsed the randomization patch code and I don't think the random calculations themselves could account for all that time.
Does anybody have a clue as to why this is happening or what I should do to debug this further?
-- Paulo Marques - www.grupopie.com
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