netdev - RE: [PATCH net-next 2/2] net: Add sysctl_reclaim

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Date: Tue, 9 May 2023 06:55:43 +0000
From: "Zhang, Cathy" <cathy.zhang@...el.com>
To: Jakub Kicinski <kuba@...nel.org>
CC: "edumazet@...gle.com" <edumazet@...gle.com>, "davem@...emloft.net"
	<davem@...emloft.net>, "pabeni@...hat.com" <pabeni@...hat.com>, "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 2/2] net: Add sysctl_reclaim_threshold



> -----Original Message-----
> From: Jakub Kicinski <kuba@...nel.org>
> Sent: Tuesday, May 9, 2023 10:05 AM
> To: Zhang, Cathy <cathy.zhang@...el.com>
> Cc: edumazet@...gle.com; davem@...emloft.net; pabeni@...hat.com;
> 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;
> netdev@...r.kernel.org
> Subject: Re: [PATCH net-next 2/2] net: Add sysctl_reclaim_threshold
> 
> On Sun,  7 May 2023 19:08:01 -0700 Cathy Zhang wrote:
> > Add a new ABI /proc/sys/net/core/reclaim_threshold which allows to
> > change the size of reserved memory from reclaiming in sk_mem_uncharge.
> > It allows to keep sk->sk_forward_alloc as small as possible when
> > system is under memory pressure, it also allows to change it larger to
> > avoid memcg charge overhead and improve performance when system is
> not
> > under memory pressure. The original reclaim threshold for reserved
> > memory per-socket is 2MB, it's selected as the max value, while the
> > default value is 64KB which is closer to the maximum size of sk_buff.
> >
> > Issue the following command as root to change the default value:
> >
> > 	echo 16384 > /proc/sys/net/core/reclaim_threshold
> 
> While we wait for Eric to pass judgment - FWIW to me it seems a bit
> overzealous to let users tune this. Does cgroup memory accounting or any
> other socket memory accounting let users control the batching parameters?

I notice the followings are allowed to be tuned:
/proc/sys/net/core/[rw]mem_default
/proc/sys/net/core/[rw]mem_max