netdev - Re: [PATCH 18/18] netvsc: call netif_receive

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: <1485297559.16328.343.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Tue, 24 Jan 2017 14:39:19 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Stephen Hemminger <stephen@...workplumber.org>
Cc:     davem@...emloft.net, kys@...rosoft.com, netdev@...r.kernel.org,
        Stephen Hemminger <sthemmin@...rosoft.com>
Subject: Re: [PATCH 18/18] netvsc: call netif_receive_skb

On Tue, 2017-01-24 at 13:06 -0800, Stephen Hemminger wrote:
> To improve performance, netvsc can call network stack directly and
> avoid the local backlog queue. This is safe since incoming packets are
> handled in softirq context already because the receive function
> callback is called from a tasklet.

Is this tasklet implementing a limit or something ?

netif_rx() queues packets to the backlog, which is processed later by
net_rx_action() like other NAPI, with limit of 64 packets per round.

Calling netif_receive_skb() means you can escape this ability to fairly
distribute the cpu cycles among multiple NAPI.

I do not see range_cnt being capped in netvsc_receive()