On 2015/10/30 17:23, Michal Hocko wrote:
On Fri 30-10-15 14:23:59, KAMEZAWA Hiroyuki wrote:
On 2015/10/30 0:17, mho...@kernel.org wrote:
[...]
@@ -3135,13 +3145,56 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int
order,
if (gfp_mask & __GFP_NORETRY)
goto noretry;
- /* Keep reclaiming pages as long as there is reasonable progress */
+ /*
+ * Do not retry high order allocations unless they are __GFP_REPEAT
+ * and even then do not retry endlessly.
+ */
pages_reclaimed += did_some_progress;
- if ((did_some_progress && order <= PAGE_ALLOC_COSTLY_ORDER) ||
- ((gfp_mask & __GFP_REPEAT) && pages_reclaimed < (1 << order))) {
- /* Wait for some write requests to complete then retry */
- wait_iff_congested(ac->preferred_zone, BLK_RW_ASYNC, HZ/50);
- goto retry;
+ if (order > PAGE_ALLOC_COSTLY_ORDER) {
+ if (!(gfp_mask & __GFP_REPEAT) || pages_reclaimed >= (1<<order))
+ goto noretry;
+
+ if (did_some_progress)
+ goto retry;
why directly retry here ?
Because I wanted to preserve the previous logic for GFP_REPEAT as much
as possible here and do an incremental change in the later patch.
I see.
[...]
@@ -3150,8 +3203,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int
order,
goto got_pg;
/* Retry as long as the OOM killer is making progress */
- if (did_some_progress)
+ if (did_some_progress) {
+ stall_backoff = 0;
goto retry;
+ }
Umm ? I'm sorry that I didn't notice page allocation may fail even
if order < PAGE_ALLOC_COSTLY_ORDER. I thought old logic ignores
did_some_progress. It seems a big change.
__alloc_pages_may_oom will set did_some_progress
So, now, 0-order page allocation may fail in a OOM situation ?
No they don't normally and this patch doesn't change the logic here.
I understand your patch doesn't change the behavior.
Looking into __alloc_pages_may_oom(), *did_some_progress is finally set by
if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL))
*did_some_progress = 1;
...depends on out_of_memory() return value.
Now, allocation may fail if oom-killer is disabled.... Isn't it complicated ?
Shouldn't we have
if (order < PAGE_ALLOC_COSTLY_ORDER)
goto retry;
here ?
Thanks,
-Kame
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