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

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Date: Wed, 10 May 2023 12:00:02 -0700
From: Shakeel Butt <shakeelb@...gle.com>
To: "Zhang, 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, Jesse" <jesse.brandeburg@...el.com>, "Srinivas, Suresh" <suresh.srinivas@...el.com>, 
	"Chen, Tim C" <tim.c.chen@...el.com>, "You, 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 Wed, May 10, 2023 at 9:09 AM Zhang, Cathy <cathy.zhang@...el.com> wrote:
>
>
[...]
> > > >
> > > > Have you tried to increase batch sizes ?
> > >
> > > I jus picked up 256 and 1024 for a try, but no help, the overhead still exists.
> >
> > This makes no sense at all.
>
> Eric,
>
> I added a pr_info in try_charge_memcg() to print nr_pages if
> nr_pages >= MEMCG_CHARGE_BATCH, except it prints 64 during the initialization
> of instances, there is no other output during the running. That means nr_pages is not
> over 64, I guess that might be the reason why to increase MEMCG_CHARGE_BATCH
> doesn't affect this case.
>

I am assuming you increased MEMCG_CHARGE_BATCH to 256 and 1024 but
that did not help. To me that just means there is a different
bottleneck in the memcg charging codepath. Can you please share the
perf profile? Please note that memcg charging does a lot of other
things as well like updating memcg stats and checking (and enforcing)
memory.high even if you have not set memory.high.