On Wed, Jan 20, 2021 at 05:21:47PM +0100, Uladzislau Rezki (Sony) wrote:
> From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
>
> This commit applies the __GFP_NOMEMALLOC gfp flag to memory allocations
> carried out by the single-argument variant of kvfree_rcu(), thus avoiding
> this can-sleep code path from dipping into the emergency reserves.
>
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>
> Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
> Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
> Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
> ---
> kernel/rcu/tree.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
> index 2014fb22644d..454809514c91 100644
> --- a/kernel/rcu/tree.c
> +++ b/kernel/rcu/tree.c
> @@ -3491,7 +3491,7 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
> if (!bnode && can_alloc) {
> krc_this_cpu_unlock(*krcp, *flags);
> bnode = (struct kvfree_rcu_bulk_data *)
> - __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN);
> + __get_free_page(GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOMEMALLOC | __GFP_NOWARN);
> *krcp = krc_this_cpu_lock(flags);
> }
>
> --
> 2.20.1
>
Please see below a V2:
V1 -> V2:
- rebase on [PATCH v2 1/1] kvfree_rcu: Directly allocate page for single-argument
- add a comment about __GFP_NOMEMALLOC usage.
<snip>
>From 1427698cdbdced53d9b5eee60aa5d22bc223056d Mon Sep 17 00:00:00 2001
From: "Paul E. McKenney" <paulmck@xxxxxxxxxx>
Date: Wed, 20 Jan 2021 17:21:47 +0100
Subject: [PATCH v2 1/1] kvfree_rcu: Use __GFP_NOMEMALLOC for single-argument
kvfree_rcu()
This commit applies the __GFP_NOMEMALLOC gfp flag to memory allocations
carried out by the single-argument variant of kvfree_rcu(), thus avoiding
this can-sleep code path from dipping into the emergency reserves.
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxx>
---
kernel/rcu/tree.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index e450c17a06b2..e7b705155c92 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3496,11 +3496,14 @@ add_ptr_to_bulk_krc_lock(struct kfree_rcu_cpu **krcp,
// view. Apart of that it forbids any OOM invoking what is
// also beneficial since we are about to release memory soon.
//
+ // __GFP_NOMEMALLOC - prevents from consuming of all the
+ // memory reserves. Please note we have a fallback path.
+ //
// __GFP_NOWARN - it is supposed that an allocation can
// be failed under low memory or high memory pressure
// scenarios.
bnode = (struct kvfree_rcu_bulk_data *)
- __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN);
+ __get_free_page(GFP_KERNEL | __GFP_NORETRY | __GFP_NOMEMALLOC | __GFP_NOWARN);
*krcp = krc_this_cpu_lock(flags);
}
--
2.20.1
<snip>
Thanks!
--
Vlad Rezki
