Benjamin LaHaise wrote:

quoted

+/*
+ * We aggressively remove defunct pgd from cr3. We execute unmap_vmas()
+ * *much* faster this way.
+ */
    

Are you switching mms in order to avoid all of the overhead associated with 
flushing an active mm during task exit?  If so, it makes much more sense to 
do this in the generic helper, as it should be a win on x86 and x86-64 
where switching to init_mm is relatively low cost given the support for 
global pages.  I'll run some tests on a couple of systems this evening and 
post the results.
  

I tried this experiment on both x86 and x86-64 and I recall not seeing 
any effect.  The mmu_gather optimization does most of this already.

Zach