(switched to email.  Please respond via emailed reply-to-all, not via the
bugzilla web interface).

On Sat, 24 Feb 2018 03:56:38 +0000 bugzilla-daemon@bugzilla.kernel.org wrote:


https://bugzilla.kernel.org/show_bug.cgi?id=198913

            Bug ID: 198913
           Summary: Swapping slows to about 20% of expected speed when
                    using multiple swap partitions on separate drives
                    (striping).

...

Problems
1) Linux's swap striping on nine drives performs at only 19.5% of the speed of
a memory-mapped file on a RAID 0 partition on the same nine drives.
2) Linux's swap striping performs best with exactly four swap partitions and
performs almost as well with just three partitions.



Well that's interesting, thanks.  Let's get this onto the mm
developers' mailing list and perhaps someone will have a theory.  And
perhaps Hugh will have a think about it when he returns to the fold.