Luck, Tony wrote:
Here are the source and disassembled binary for the lock/unlock routines modified as suggested by Linus to fit the lock word back into 32-bits. Performance for lock/unlock time in the uncontended in-cache case is a little worse (another 8% on top of the 8% I'd already givenup compared to the original "xchg" version).
Youch, that is 17% if I've done the math correctly. This is to deal with contended locks more "fairly" correct?
I haven't tried a macro-level benchmark yet to see whether this makes it noticeable.
Not exactly macro with a big M, but something like netperf aggregate TCP_RR would probably do a fair bit of lock/unlock exercise.
Taking ftp://ftp.netperf.org/netperf/netperf-2.4.5.tar.bz2 then tar xjf netperf-2.4.5-tar.bz2 cd netperf-2.4.5 ./configure --enable-burst --prefix=<your choice> make install netserverand then it should be possible to see what the max single-connection, single-byte, aggregate TCP_RR perf is with something like:
for b in 0 1 4 16 64 256 do netperf -t TCP_RR -i 30,3 -P 0 -B "burst $b" -- -r 1 -D -b $b donewhere the values for b can be as you choose - 0 means no additional transaction in flight at one time, so just the one synchronous transaction. The -i 30,3 means repeat each data point at least 3 times but no more than 30 to get the default confidence interval of 99% confident the result is within +/- 2.5% (you can make that stricter with -I 99,N where N is 2x the +/- you want). The -P 0 tells netperf to omit the test banner (makes the output more readable). The -B is a user supplied tag emitted with the result. The options after the "--" are test-specific - in this case -r 1 means request and response size of 1 byte, -D means set TCP_NODELAY and the -b $b means add an additional $b transactions in flight at one time on the connection.
You may need/want to mess with a global (before the "--") -T option to bind netperf/netserver to specific cores:
-T N # both netperf and netserver to core N on their respective systems -T N, # just netperf to core N, netserver floats -T ,M # netperf floats, netserver to core M -T N,M # netperf to N, netserver to MOnce you have come-up with the peak setting for the -b option, you can then do a variation on the theme to run multiple, concurrent netperfs:
for i in 1 2 ... do netperf -t TCP_RR -i 30 -P 0 -- -r 1 -D -b <burst> & donewhere now each backgrounded netperf will run 30 iterations no matter what - you may still want to mess about with the scripting and bind netperf/netserver as you wish, or not. I find the binding helps make things more repeatable.
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