Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: smp overhead, and rwlocks considered harmful | From | Alan Cox <> | Date | 23 Mar 2003 15:17:51 +0000 |
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On Sun, 2003-03-23 at 12:33, Michael Vergoz wrote: > Hi Andrew, > > I would like to noticed to you that the SMP capacity can't be used on one process under Linux. > > when you run 'time dd if=/dev/zero of=foo bs=1 count=1M', the capacity of 1 processor will > use since your command sets is executed in ONE process.
Your dd is benchmarking the lock operations in the C library I suspect. The kernel will happily use both processors and a given syscall can evne start on one cpu and complete on another, or have the IRQ tasks executed on its behalf on another CPU.
There are *good* reasons btw for avoiding splitting stuff too far, the cost of copying data between processor caches is very high.
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