netdev - Re: [WIP] net+mlx4: auto doorbell

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]

Date:   Wed, 30 Nov 2016 18:50:55 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Tom Herbert <tom@...bertland.com>
Cc:     Jesper Dangaard Brouer <brouer@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Rick Jones <rick.jones2@....com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Achiad Shochat <achiad@...lanox.com>
Subject: Re: [WIP] net+mlx4: auto doorbell

On Wed, 2016-11-30 at 18:32 -0800, Eric Dumazet wrote:

> I simply suggest we try to queue the qdisc for further servicing as we
> do today, from net_tx_action(), but we might use a different bit, so
> that we leave the opportunity for another cpu to get __QDISC_STATE_SCHED
> before we grab it from net_tx_action(), maybe 100 usec later (time to
> flush all skbs queued in napi_consume_skb() and maybe RX processing,
> since most NIC handle TX completion before doing RX processing from thei
> napi poll handler.
> 
> Should be doable with few changes in __netif_schedule() and
> net_tx_action(), plus some control paths that will need to take care of
> the new bit at dismantle time, right ?

Hmm... this is silly. Code already implements a different bit.

qdisc_run() seems to run more often from net_tx_action(), I have to find
out why.