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[35.236.235.116]) by smtp.gmail.com with UTF8SMTPSA id 956f58d0204a3-6433c48472dsm2702283d50.22.2025.11.29.09.06.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Sat, 29 Nov 2025 09:06:51 -0800 (PST) Date: Sat, 29 Nov 2025 12:06:51 -0500 From: Willem de Bruijn To: Eric Dumazet , John Stultz , Thomas Gleixner , Stephen Boyd , Jakub Kicinski , Paolo Abeni Cc: linux-kernel , netdev@vger.kernel.org, Eric Dumazet , Eric Dumazet , Kevin Yang , Willem de Bruijn , Neal Cardwell , Yuchung Cheng Message-ID: In-Reply-To: <20251129095740.3338476-1-edumazet@google.com> References: <20251129095740.3338476-1-edumazet@google.com> Subject: Re: [PATCH] time/timecounter: inline timecounter_cyc2time() Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Eric Dumazet 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 > Link: https://research.google/pubs/swift-delay-is-simple-and-effective-for-congestion-control-in-the-datacenter/ > Cc: Kevin Yang > Cc: Willem de Bruijn > Cc: Neal Cardwell > Cc: Yuchung Cheng Reviewed-by: Willem de Bruijn