From: Stephen Brennan stephen.s.brennan@oracle.com
Commit 93b3a674485f6a4b8ffff85d1682d5e8b7c51560 upstream
Commit 93b3a674485f ("mm,vmstat: reduce zone->lock holding time by /proc/pagetypeinfo") upstream caps the number of iterations over each free_list at 100,000, and also drops the zone->lock in between each migrate type. Capping the iteration count alters the file contents in some cases, which means this approach may not be suitable for stable backports.
However, dropping zone->lock in between migrate types (and, as a result, page orders) will not change the /proc/pagetypeinfo file contents. It can significantly reduce the length of time spent with IRQs disabled, which can prevent missed interrupts or soft lockups which we have observed on systems with particularly large memory.
Thus, this commit is a modified version of the upstream one which only drops the lock in between migrate types.
Fixes: 467c996c1e19 ("Print out statistics in relation to fragmentation avoidance to /proc/pagetypeinfo") Signed-off-by: Stephen Brennan stephen.s.brennan@oracle.com Reviewed-by: Aruna Ramakrishna aruna.ramakrishna@oracle.com Reviewed-by: Khalid Aziz khalid.aziz@oracle.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- mm/vmstat.c | 3 +++ 1 file changed, 3 insertions(+)
--- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -973,6 +973,9 @@ static void pagetypeinfo_showfree_print( list_for_each(curr, &area->free_list[mtype]) freecount++; seq_printf(m, "%6lu ", freecount); + spin_unlock_irq(&zone->lock); + cond_resched(); + spin_lock_irq(&zone->lock); } seq_putc(m, '\n'); }