linux-kernel - Re: [PATCH] time/timecounter: inline timecounter

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: <CAL+tcoAS9u1A9xpsWaAzSojJ7qepWsvF3imC5LtEhu=zD9AjsQ@mail.gmail.com>
Date: Tue, 20 Jan 2026 16:18:27 +0800
From: Jason Xing <kerneljasonxing@...il.com>
To: Eric Dumazet <edumazet@...gle.com>
Cc: John Stultz <jstultz@...gle.com>, Thomas Gleixner <tglx@...utronix.de>, 
	Stephen Boyd <sboyd@...nel.org>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, 
	linux-kernel <linux-kernel@...r.kernel.org>, netdev@...r.kernel.org, 
	Eric Dumazet <eric.dumazet@...il.com>, Kevin Yang <yyd@...gle.com>, 
	Willem de Bruijn <willemb@...gle.com>, Neal Cardwell <ncardwell@...gle.com>, 
	Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH] time/timecounter: inline timecounter_cyc2time()

On Sat, Nov 29, 2025 at 5:57 PM Eric Dumazet <edumazet@...gle.com> wrote:
>
> New network transport protocols want NIC drivers to get hwtstamps
> of all incoming packets, and possibly all outgoing packets.
>
> Swift congestion control is used by good old TCP transport and is
> our primary need for timecounter_cyc2time(). This will be upstreamed soon.
>
> This means timecounter_cyc2time() can be called more than 100 million
> times per second on a busy server.
>
> Inlining timecounter_cyc2time() brings a 12 % improvement on a
> UDP receive stress test on a 100Gbit NIC.
>
> Note that FDO, LTO, PGO are unable to magically help for this
> case, presumably because NIC drivers are almost exclusively shipped
> as modules.
>
> Add an unlikely() around the cc_cyc2ns_backwards() case,
> even if FDO (when used) is able to take care of this optimization.
>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
> Link: https://research.google/pubs/swift-delay-is-simple-and-effective-for-congestion-control-in-the-datacenter/
> Cc: Kevin Yang <yyd@...gle.com>
> Cc: Willem de Bruijn <willemb@...gle.com>
> Cc: Neal Cardwell <ncardwell@...gle.com>
> Cc: Yuchung Cheng <ycheng@...gle.com>

When I'm browsing the modification related to SWIFT, I noticed this
patch seems to have not been merged yet?

Thanks,
Jason