After switching from the 13.2 release to the Tumbleweed release, I noticed a
significant increase in page load times with Firefox. In addition, page reload
times did not decrease even though many items on the page are in the browser
cache. The same did not occur with Chromium, for example.

Steps to reproduce:

Install Firefox; leave its 'config' settings unmodified from the distro
packages. In this case, Firefox was on release 42.0 after switching to
Tumbleweed and later updated to 44.0.2 when trying to debug this issue.

Open Firebug or the built-in Firefox developer toolbox; enable the network tab.
Load a page in browser; does not matter the URL. Observe the time to load and
reload the page, paying particular emphasis to the start time to load each
cache item.

Expected results:

Based on the Mozilla documentation and other online sources, my understanding
is the cache items should not incur time for: blocking, DNS lookup, connecting,
sending, waiting and receiving (although there is a positive value shown for
waiting time). Further, most of these items should be 'loaded' essentially
concurrently (which corresponds to zero times for each task [excluding waiting]
mentioned in previous sentence).

Actual results:

On page reload or any page load that involves cache items, there are staggered
start times on each cache item and a lack of time reduction (compared to
loading the items for the first time). The cache items are not 'loaded'
immediately and concurrently but are staggered, with each subsequent cache item
having a later 'request start time since the beginning' (as titled in Firebug)
with the delta being roughly equal to the 'waiting' time of the previous item.

The end result is a much slower page load, with the delay being 100-500% the
time to perform all the other tasks. Example: page loads in 6 seconds versus 1
second.

Basis for claim:

I have other computers running openSUSE release 13.2 and Firefox release 39.0
and 41.0.2, respectively. Neither exhibits the staggered cache loading nor
overall page load issue described above.

>From the Mozilla ftp site, I downloaded these binary releases of Firefox:

39.0
41.0.2
42.0
43.0.2
44.0.2

to the "box running openSUSE Tumbleweed and Firefox 44.0.2" and ran each binary
on a set of pages from a single site. The timings were consistent in all
releases and did not exhibit the staggered start times on each cache item on
either initial page load or reload. Running release 44.0.2 from the distro
packages continues to exhibit the staggered start times on each cache item and
lack of time reduction on page reload.