netdev - Re: [PATCH net-next 0/5] implement kthread based napi poll

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: <20200930130839.427eafa9@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 30 Sep 2020 13:08:39 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Wei Wang <weiwan@...gle.com>
Cc:     "David S . Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        Hannes Frederic Sowa <hannes@...essinduktion.org>,
        Paolo Abeni <pabeni@...hat.com>, Felix Fietkau <nbd@....name>
Subject: Re: [PATCH net-next 0/5] implement kthread based napi poll

On Wed, 30 Sep 2020 12:21:35 -0700 Wei Wang wrote:
> With napi poll moved to kthread, scheduler is in charge of scheduling both
> the kthreads handling network load, and the user threads, and is able to
> make better decisions. In the previous benchmark, if we do this and we
> pin the kthreads processing napi poll to specific CPUs, scheduler is
> able to schedule user threads away from these CPUs automatically.
> 
> And the reason we prefer 1 kthread per napi, instead of 1 workqueue
> entity per host, is that kthread is more configurable than workqueue,
> and we could leverage existing tuning tools for threads, like taskset,
> chrt, etc to tune scheduling class and cpu set, etc. Another reason is
> if we eventually want to provide busy poll feature using kernel threads
> for napi poll, kthread seems to be more suitable than workqueue. 

As I said in my reply to the RFC I see better performance with the
workqueue implementation, so I would hold off until we have more
conclusive results there, as this set adds fairly strong uAPI that 
we'll have to support for ever.