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I'm reading http://lse.sourceforge.net/locking/dcache/dcache_lock.html, in which spinlock time for each functions is measured:
SPINLOCKS HOLD WAIT
UTIL CON MEAN( MAX ) MEAN( MAX )(% CPU) TOTAL NOWAIT SPIN RJECT NAME
5.3% 16.5% 0.6us(2787us) 5.0us(3094us)(0.89%) 15069563 83.5% 16.5% 0% dcache_lock
0.01% 10.9% 0.2us( 7.5us) 5.3us( 116us)(0.00%) 119448 89.1% 10.9% 0% d_alloc+0x128
0.04% 14.2% 0.3us( 42us) 6.3us( 925us)(0.02%) 233290 85.8% 14.2% 0% d_delete+0x10
0.00% 3.5% 0.2us( 3.1us) 5.6us( 41us)(0.00%) 5050 96.5% 3.5% 0% d_delete+0x94
I'd like to know where these statistics are from. I tried oprofile, but it seems oprofile cannot measure lock holding and waiting time for a specific lock. And valgrind's drd slows down applications too much, which will make the result less accurate and also consume too much time. mutrace seems good, but as the name points out, I'm afraid it can only trace mutex exclusions.
So is there any other tool, or how to use the tools I mentioned above, to get lock contention statistics?
Thanks for your reply.
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Lock contention takes place when a thread tries to acquire the lock to an object which is already acquired by other thread*. Until the object is released, the thread is blocked (in other words, it is in the Waiting state).
Contention. Attempting to lock an already locked mutex is called contention. In a well-planned program, contention should be quite low. You should design your code so that most attempts to lock the mutex will not block.
Lock contention occurs when a thread is trying to enter the synchronized block/method currently executed by another thread. This second thread is now forced to wait until the first thread has completed executing the synchronized block and releases the monitor.
Finally I find the performance measuring tool used in the article, which needs to patch kernel .
The introduction page can be found at http://oss.sgi.com/projects/lockmeter/, and the latest kernel patch corresponds to kernel version 2.6.16, which you can download here.
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