Any thoughts on why 'file-backed DB caching' is causing such a problem
under 2.2 as compared to 2.1?
Isn't it that 2.2 has higher write overhead than 2.1 and hence the
'shared memory DB caching'
has higher impact than the 'file-backed DB caching' on their performances
? Assuming no swapping, continuous writes to a shared memory region can
be performed without disk
access, while writes to the named memory mapping can cause writeback of
dirty pages if the number
of dirty pages goes beyond a threshold. Since slapadding produces a lot
of dirty pages, continuous
disk write activities would be observed with the 'file-backed DB caching'.