On Wed, Apr 01, 2020 at 03:32:38PM -0400, Pavel Tatashin wrote:
> Initializing struct pages is a long task and keeping interrupts disabled
> for the duration of this operation introduces a number of problems.
>
> 1. jiffies are not updated for long period of time, and thus incorrect time
> is reported. See proposed solution and discussion here:
> lkml/20200311123848.118638-1-shile.zhang@xxxxxxxxxxxxxxxxx
> 2. It prevents farther improving deferred page initialization by allowing
not allowing
> inter-node multi-threading.
intra-node
...
> After:
> [ 1.632580] node 0 initialised, 12051227 pages in 436ms
Fixes: 3a2d7fa8a3d5 ("mm: disable interrupts while initializing deferred pages")
Reported-by: Shile Zhang <shile.zhang@xxxxxxxxxxxxxxxxx>
> Signed-off-by: Pavel Tatashin <pasha.tatashin@xxxxxxxxxx>
Freezing jiffies for a while during boot sounds like stable to me, so
Cc: <stable@xxxxxxxxxxxxxxx> [4.17.x+]
Can you please add a comment to mmzone.h above node_size_lock, something like
* Must be held any time you expect node_start_pfn,
* node_present_pages, node_spanned_pages or nr_zones to stay constant.
+ * Also synchronizes pgdat->first_deferred_pfn during deferred page
+ * init.
...
spinlock_t node_size_lock;
> @@ -1854,18 +1859,6 @@ deferred_grow_zone(struct zone *zone, unsigned int order)
> return false;
>
> pgdat_resize_lock(pgdat, &flags);
> -
> - /*
> - * If deferred pages have been initialized while we were waiting for
> - * the lock, return true, as the zone was grown. The caller will retry
> - * this zone. We won't return to this function since the caller also
> - * has this static branch.
> - */
> - if (!static_branch_unlikely(&deferred_pages)) {
> - pgdat_resize_unlock(pgdat, &flags);
> - return true;
> - }
> -
Huh, looks like this wasn't needed even before this change.
The rest looks fine.
Reviewed-by: Daniel Jordan <daniel.m.jordan@xxxxxxxxxx>
