* [PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER
@ 2018-11-01 17:37 Konstantin Khlebnikov
2018-11-02 8:55 ` Michal Hocko
0 siblings, 1 reply; 2+ messages in thread
From: Konstantin Khlebnikov @ 2018-11-01 17:37 UTC (permalink / raw)
To: linux-mm, Andrew Morton, Michal Hocko, linux-kernel
Page allocator has check in __alloc_pages_slowpath() but nowdays
there is earlier entry point into reclimer without such check:
get_page_from_freelist() -> node_reclaim().
Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
mm/vmscan.c | 6 ++++++
1 file changed, 6 insertions(+)
diff --git a/mm/vmscan.c b/mm/vmscan.c
index 62ac0c488624..52f672420f0b 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -4117,6 +4117,12 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
{
int ret;
+ /*
+ * Do not scan if allocation will never succeed.
+ */
+ if (order >= MAX_ORDER)
+ return NODE_RECLAIM_NOSCAN;
+
/*
* Node reclaim reclaims unmapped file backed pages and
* slab pages if we are over the defined limits.
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER
2018-11-01 17:37 [PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER Konstantin Khlebnikov
@ 2018-11-02 8:55 ` Michal Hocko
0 siblings, 0 replies; 2+ messages in thread
From: Michal Hocko @ 2018-11-02 8:55 UTC (permalink / raw)
To: Konstantin Khlebnikov; +Cc: linux-mm, Andrew Morton, linux-kernel
On Thu 01-11-18 20:37:52, Konstantin Khlebnikov wrote:
> Page allocator has check in __alloc_pages_slowpath() but nowdays
> there is earlier entry point into reclimer without such check:
> get_page_from_freelist() -> node_reclaim().
Is the order check so expensive that it would be visible in the fast
path? Spreading these MAX_ORDER checks sounds quite fragile to me.
> Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
> ---
> mm/vmscan.c | 6 ++++++
> 1 file changed, 6 insertions(+)
>
> diff --git a/mm/vmscan.c b/mm/vmscan.c
> index 62ac0c488624..52f672420f0b 100644
> --- a/mm/vmscan.c
> +++ b/mm/vmscan.c
> @@ -4117,6 +4117,12 @@ int node_reclaim(struct pglist_data *pgdat, gfp_t gfp_mask, unsigned int order)
> {
> int ret;
>
> + /*
> + * Do not scan if allocation will never succeed.
> + */
> + if (order >= MAX_ORDER)
> + return NODE_RECLAIM_NOSCAN;
> +
> /*
> * Node reclaim reclaims unmapped file backed pages and
> * slab pages if we are over the defined limits.
>
--
Michal Hocko
SUSE Labs
^ permalink raw reply [flat|nested] 2+ messages in thread
end of thread, other threads:[~2018-11-02 8:56 UTC | newest]
Thread overview: 2+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-11-01 17:37 [PATCH RFC] mm: do not start node_reclaim for page order > MAX_ORDER Konstantin Khlebnikov
2018-11-02 8:55 ` Michal Hocko
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).