linux-kernel - Re: [PATCH RFC] net: memcg accounting for veth devices

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Date:   Tue, 1 Mar 2022 13:31:20 -0800
From:   Luis Chamberlain <mcgrof@...nel.org>
To:     "Eric W. Biederman" <ebiederm@...ssion.com>
Cc:     Shakeel Butt <shakeelb@...gle.com>,
        Colin Ian King <colin.king@...onical.com>,
        NeilBrown <neilb@...e.de>, Vasily Averin <vvs@...tuozzo.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Michal Hocko <mhocko@...e.com>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Linux MM <linux-mm@...ck.org>, netdev@...r.kernel.org,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, Tejun Heo <tj@...nel.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>, linux-kernel@...r.kernel.org,
        kernel@...nvz.org
Subject: Re: [PATCH RFC] net: memcg accounting for veth devices

On Tue, Mar 01, 2022 at 01:25:16PM -0800, Luis Chamberlain wrote:
> diff --git a/kernel/ucount.c b/kernel/ucount.c
> index 4f5613dac227..980ffaba1ac5 100644
> --- a/kernel/ucount.c
> +++ b/kernel/ucount.c
> @@ -238,6 +238,8 @@ struct ucounts *inc_ucount(struct user_namespace *ns, kuid_t uid,
>  		long max;
>  		tns = iter->ns;
>  		max = READ_ONCE(tns->ucount_max[type]);
> +		if (atomic_long_read(&iter->ucount[type]) > max/16)
> +			cond_resched();
>  		if (!atomic_long_inc_below(&iter->ucount[type], max))
>  			goto fail;

You can of course ignore this, it was just a hack to try to avoid
a soft lockup on the workqueues.

  Luis