netdev - Re: [PATCH net-next 1/2] net: Keep sk->sk_forward

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Message-ID: <20230511211338.oi4xwoueqmntsuna@google.com>
Date: Thu, 11 May 2023 21:18:42 +0000
From: Shakeel Butt <shakeelb@...gle.com>
To: Zhang@...gle.com, Cathy <cathy.zhang@...el.com>
Cc: Eric Dumazet <edumazet@...gle.com>, Linux MM <linux-mm@...ck.org>, 
	Cgroups <cgroups@...r.kernel.org>, Paolo Abeni <pabeni@...hat.com>, 
	"davem@...emloft.net" <davem@...emloft.net>, "kuba@...nel.org" <kuba@...nel.org>, Brandeburg@...gle.com, 
	Jesse <jesse.brandeburg@...el.com>, Srinivas@...gle.com, 
	Suresh <suresh.srinivas@...el.com>, Chen@...gle.com, Tim C <tim.c.chen@...el.com>, 
	You@...gle.com, Lizhen <lizhen.you@...el.com>, 
	"eric.dumazet@...il.com" <eric.dumazet@...il.com>, "netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 1/2] net: Keep sk->sk_forward_alloc as a proper size

On Thu, May 11, 2023 at 09:26:46AM +0000, Zhang, Cathy wrote:
> 
[...]
> 
>      8.98%  mc-worker        [kernel.vmlinux]          [k] page_counter_cancel
>             |
>              --8.97%--page_counter_cancel
>                        |
>                         --8.97%--page_counter_uncharge
>                                   drain_stock
>                                   __refill_stock
>                                   refill_stock
>                                   |
>                                    --8.91%--try_charge_memcg
>                                              mem_cgroup_charge_skmem

I do want to understand for above which specific condition in
__refill_stock is causing to drain stock in the charge code path. Can
you please re-run and profile your test with following code snippet (or
use any other mechanism which can answer the question)?

>From f1d91043f21f4b29717c78615b374d79fc021d1f Mon Sep 17 00:00:00 2001
From: Shakeel Butt <shakeelb@...gle.com>
Date: Thu, 11 May 2023 20:00:19 +0000
Subject: [PATCH] Debug drain on charging.

---
 mm/memcontrol.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index d31fb1e2cb33..4c1c3d90a4a3 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2311,6 +2311,16 @@ static void drain_local_stock(struct work_struct *dummy)
 		obj_cgroup_put(old);
 }
 
+static noinline void drain_stock_1(struct memcg_stock_pcp *stock)
+{
+	drain_stock(stock);
+}
+
+static noinline void drain_stock_2(struct memcg_stock_pcp *stock)
+{
+	drain_stock(stock);
+}
+
 /*
  * Cache charges(val) to local per_cpu area.
  * This will be consumed by consume_stock() function, later.
@@ -2321,14 +2331,14 @@ static void __refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
 
 	stock = this_cpu_ptr(&memcg_stock);
 	if (READ_ONCE(stock->cached) != memcg) { /* reset if necessary */
-		drain_stock(stock);
+		drain_stock_1(stock);
 		css_get(&memcg->css);
 		WRITE_ONCE(stock->cached, memcg);
 	}
 	stock->nr_pages += nr_pages;
 
 	if (stock->nr_pages > MEMCG_CHARGE_BATCH)
-		drain_stock(stock);
+		drain_stock_2(stock);
 }
 
 static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages)
-- 
2.40.1.606.ga4b1b128d6-goog