[BUG, bisect] hrtimer: severe lag after suspend & resume

[Jeremiah Mahler]

all,

After a fresh boot, the Chrome web browser behaves normally.  Pages
load quickly and scroll fast.  Even image heavy sites such as
images.google.com work fine.  However, after a suspend and resume
cycle, Chrome becomes very slow.  Pages take ten seconds or more to
load.  The scroll bars and buttons are almost completely
unresponsive.  Interestingly, I can run Firefox on the same sites
and it has no issue whatsoever.

I have bisected the kernel and found that the following commit
introduced the bug.  It is present in the latest linux-next (20150602).

  From 868a3e915f7f5eba8f8cb4f7da2276760807c51c Mon Sep 17 00:00:00 2001
  From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
  Date: Tue, 14 Apr 2015 21:08:37 +0000
  Subject: [PATCH] hrtimer: Make offset update smarter
  
  On every tick/hrtimer interrupt we update the offset variables of the
  clock bases. That's silly because these offsets change very seldom.
  
  Add a sequence counter to the time keeping code which keeps track of
  the offset updates (clock_was_set()). Have a sequence cache in the
  hrtimer cpu bases to evaluate whether the offsets must be updated or
  not. This allows us later to avoid pointless cacheline pollution.
  
  Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
  Reviewed-by: Preeti U Murthy <preeti@xxxxxxxxxxxxxxxxxx>
  Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
  Cc: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
  Cc: Marcelo Tosatti <mtosatti@xxxxxxxxxx>
  Cc: Frederic Weisbecker <fweisbec@xxxxxxxxx>
  Cc: John Stultz <john.stultz@xxxxxxxxxx>
  Link: http://lkml.kernel.org/r/20150414203501.132820245@xxxxxxxxxxxxx
  Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
  Cc: John Stultz <john.stultz@xxxxxxxxxx>
  ---
   include/linux/hrtimer.h             |  4 ++--
   include/linux/timekeeper_internal.h |  2 ++
   kernel/time/hrtimer.c               |  3 ++-
   kernel/time/timekeeping.c           | 23 ++++++++++++++++-------
   kernel/time/timekeeping.h           |  7 ++++---
   5 files changed, 26 insertions(+), 13 deletions(-)

-- 
- Jeremiah Mahler
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