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SubjectRe: (*(unsigned long *)&jiffies)++;
On Fri, 7 Jan 2000, Petko Manolov wrote:

>Lock don't hurt anyway.

Locks definitely _hurt_ performance very badly. Locks don't scale in SMP
so if you lock the bus all the time only once CPU between the NR_CPUS will
run and the other will stall at the first memory bus access. Locks also
prevents the locking-CPU to reorder instructions on IA32. locks hurt also
in UP for this reason.

>May be i am not right, but i think there was some simple instructions
>(not only incl) that force lock before them in both cases.

You are talking about xchg (and it's 64bit variant) but they are
unrelated.

Andrea


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