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Message-Id: <20170517.160622.1668271289507037704.davem@davemloft.net> Date: Wed, 17 May 2017 16:06:22 -0400 (EDT) From: David Miller <davem@...emloft.net> To: edumazet@...gle.com Cc: ncardwell@...gle.com, ycheng@...gle.com, soheil@...gle.com, weiwan@...gle.com, netdev@...r.kernel.org, eric.dumazet@...il.com Subject: Re: [PATCH net-next 00/15] tcp: TCP TS option use 1 ms clock From: Eric Dumazet <edumazet@...gle.com> Date: Tue, 16 May 2017 13:59:59 -0700 > TCP Timestamps option is defined in RFC 7323 > > Traditionally on linux, it has been tied to the internal > 'jiffy' variable, because it had been a cheap and good enough > generator. > > Unfortunately some distros use HZ=250 or even HZ=100 leading > to not very useful TCP timestamps. > > For TCP flows in the DC, Google has used usec resolution for more > than two years with great success [1]. > RCVBUF autotuning is more precise. > > This series converts tp->tcp_mstamp to a plain u64 value storing > a 1 usec TCP clock. > > This choice will allow us to upstream the 1 usec TS option as > discussed in IETF 97. > > Kathleen Nichols [2] and others advocate for 1ms TS clocks for > network analysis. (1ms being the lowest value supported by RFC 7323.) > > [1] https://www.ietf.org/proceedings/97/slides/slides-97-tcpm-tcp-options-for-low-latency-00.pdf > [2] http://netseminar.stanford.edu/seminars/02_02_17.pdf Series applied, thanks Eric.
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