Re: [PATCH 1/5] cpuset memory spread basic implementation

[Andrew Morton]

Paul Jackson <pj@xxxxxxx> wrote:
>
> This policy can provide substantial improvements for jobs that
>  need to place thread local data on the corresponding node, but
>  that need to access large file system data sets that need to
>  be spread across the several nodes in the jobs cpuset in order
>  to fit.  Without this patch, especially for jobs that might
>  have one thread reading in the data set, the memory allocation
>  across the nodes in the jobs cpuset can become very uneven.


It all seems rather ironic.  We do vast amounts of development to make
certain microbenchmarks look good, then run a real workload on the thing,
find that all those microbenchmark-inspired tweaks actually deoptimised the
real workload?  So now we need to add per-task knobs to turn off the
previously-added microbenchmark-tweaks.

What happens if one process does lots of filesystem activity and another
one (concurrent or subsequent) wants lots of thread-local storage?  Won't
the same thing happen?

IOW: this patch seems to be a highly specific bandaid which is repairing an
ill-advised problem of our own making, does it not?
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