Re: [PATCH v3] mm: fix tick timer stall during deferred page init

[Daniel Jordan]

On Thu, Mar 19, 2020 at 03:05:12PM -0400, Daniel Jordan wrote:
> Regardless,
> Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>

Darn, I spoke too soon.

On a two-socket Xeon, smaller values of TICK_PAGE_COUNT caused the deferred
init timestamp to grow by over 25%.  This was with pgdatinit0 bound to the
timer interrupt CPU to make sure the issue always reproduces.

               TICK_PAGE_COUNT     node 0 deferred
                                   init time (ms)
               ---------------     ---------------
                          4096                 610
                          8192                 587
                         16384                 487
                         32768                 480    // used in the patch

Instead of trying to find a constant that lets the timer interrupt run often
enough, I think a better way forward is to reconsider how we handle the resize
lock.  I plan to prototype something and reply back with what I get.