netdev - Re: [RFC PATCH 1/2] net: Add sysfs files for threaded NAPI.

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 for Android: free password hash cracker in your pocket

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

Message-ID: <20230524085507.3f38c758@kernel.org>
Date: Wed, 24 May 2023 08:55:07 -0700
From: Jakub Kicinski <kuba@...nel.org>
To: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, Kurt
 Kanzenbach <kurt.kanzenbach@...utronix.de>, Paolo Abeni
 <pabeni@...hat.com>, Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [RFC PATCH 1/2] net: Add sysfs files for threaded NAPI.

On Wed, 24 May 2023 13:12:58 +0200 Sebastian Andrzej Siewior wrote:
> I've been looking into threaded NAPI. One awkward thing to do is
> to figure out the thread names, pids in order to adjust the thread
> priorities and SMP affinity.
> On PREEMPT_RT the NAPI thread is treated (by the user) the same way as
> the threaded interrupt which means a dedicate CPU affinity for the
> thread and a higher task priority to be favoured over other tasks on the
> CPU. Otherwise the NAPI thread can be preempted by other threads leading
> to delays in packet delivery.
> Having to run ps/ grep is awkward to get the PID right. It is not easy
> to match the interrupt since there is no obvious relation between the
> IRQ and the NAPI thread.
> NAPI threads are enabled often to mitigate the problems caused by a
> "pending" ksoftirqd (which has been mitigated recently by doing softiqrs
> regardless of ksoftirqd status). There is still the part that the NAPI
> thread does not use softnet_data::poll_list.

This needs to go to the netdev netlink family, not sysfs.
There's much more information about NAPI to expose and sysfs will
quickly start showing its limitations.