Re: [PATCH 00/20] staging: lustre: convert to rhashtable

From: Greg Kroah-Hartman
Date: Mon Apr 23 2018 - 09:08:51 EST

On Thu, Apr 12, 2018 at 07:54:48AM +1000, NeilBrown wrote:
> libcfs in lustre has a resizeable hashtable.
> Linux already has a resizeable hashtable, rhashtable, which is better
> is most metrics. See in a few days
> for an introduction to rhashtable.
> This series converts lustre to use rhashtable. This affects several
> different tables, and each is different is various ways.
> There are two outstanding issues. One is that a bug in rhashtable
> means that we cannot enable auto-shrinking in one of the tables. That
> is documented as appropriate and should be fixed soon.
> The other is that rhashtable has an atomic_t which counts the elements
> in a hash table. At least one table in lustre went to some trouble to
> avoid any table-wide atomics, so that could lead to a regression.
> I'm hoping that rhashtable can be enhanced with the option of a
> per-cpu counter, or similar.
> I have enabled automatic shrinking on all tables where it makes sense
> and doesn't trigger the bug. I have also removed all hints concerning
> min/max size - I cannot see how these could be useful.
> The dump_pgcache debugfs file provided some interesting challenges. I
> think I have cleaned it up enough so that it all makes sense. An
> extra pair of eyes examining that code in particular would be
> appreciated.
> This series passes all the same tests that pass before the patches are
> applied.

I've taken the first 4 patches of this series, as they were "obviously
correct". I'll let you and James argue about the rest. Feel free to
resend when there's some sort of agreement.


greg k-h