I don't think individual dentry counters are as much a problem as
acquisition of dcache_lock for every path component lookup as done
by the earlier path walking algorithm. The big deal with fastwalk
is that it decreases the number of acquisitions of dcache_lock
for a webserver workload by 70% on an 8-CPU machine. That is avoiding
a lot of possible cacheline bouncing of dcache_lock.
> > In any case, we all know often acquired global locks are a bad idea
> > on a 32-way, and should be avoided like the plague. I just wish we
> > had a dcache solution that didn't even need locks as much... :)
> Well, avoiding data corruption is a preferable goal too. The point of
> RCU is not to have to take a lock for the common read case. I'd expect
> good results from it on the NUMA machines - never been benchmarked, as
> far as I recall.
You can see that in wli's dbench 512 results on his NUMA box.
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