netdev - Re: [PATCH v2 net-next] net: generalize skb freeing deferral to per-cpu lists

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <2c092f98a8fe1702173fe2b4999811dd2263faf3.camel@redhat.com>
Date:   Tue, 26 Apr 2022 09:38:22 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Eric Dumazet <eric.dumazet@...il.com>,
        "David S . Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     netdev <netdev@...r.kernel.org>, Eric Dumazet <edumazet@...gle.com>
Subject: Re: [PATCH v2 net-next] net: generalize skb freeing deferral to
 per-cpu lists


Hello,

I'm sorry for the late feedback. I have only a possibly relevant point
below.

On Fri, 2022-04-22 at 13:12 -0700, Eric Dumazet wrote:
[...]
> @@ -6571,6 +6577,28 @@ static int napi_threaded_poll(void *data)
>  	return 0;
>  }
>  
> +static void skb_defer_free_flush(struct softnet_data *sd)
> +{
> +	struct sk_buff *skb, *next;
> +	unsigned long flags;
> +
> +	/* Paired with WRITE_ONCE() in skb_attempt_defer_free() */
> +	if (!READ_ONCE(sd->defer_list))
> +		return;
> +
> +	spin_lock_irqsave(&sd->defer_lock, flags);
> +	skb = sd->defer_list;

I *think* that this read can possibly be fused with the previous one,
and another READ_ONCE() should avoid that.

BTW it looks like this version gives slightly better results than the
previous one, perhpas due to the single-liked list usage?

Thanks!

Paolo