Date: Mon, 26 Sep 2011 09:17:43 -0400 From: John Baldwin <jhb@freebsd.org> To: freebsd-current@freebsd.org Cc: Adrian Chadd <adrian@freebsd.org>, Alexander Motin <mav@freebsd.org> Subject: Re: ath / 802.11n performance issues and timer code Message-ID: <201109260917.44236.jhb@freebsd.org> In-Reply-To: <CAJ-Vmo=kScoove4_dvj_-LS%2BWnWhF4aWU9FrWF4=5kYr06-AoA@mail.gmail.com> References: <CAJ-VmomZyDJV62yCQOvG=UB6H4wfz9=3_cWzEL7vWAA14TCyYA@mail.gmail.com> <4E7D6700.4080302@FreeBSD.org> <CAJ-Vmo=kScoove4_dvj_-LS%2BWnWhF4aWU9FrWF4=5kYr06-AoA@mail.gmail.com>
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On Sunday, September 25, 2011 5:48:31 am Adrian Chadd wrote: > Nope, it has the opposite effect: > > * Increased latency may make aggregation better (for TX) but it limits > throughput because TCP senses a latency increase; I suspect this matters more. Have you tried comparing UDP throughput in the two cases? One behavioral difference of a periodic timer vs a deadline timer is that if you ask to delay for "1 clock tick", that can be anywhere from 0us to 1000us (with hz == 1000) when using the periodic timer (because you can set the callout at any time within a tick, but the callout will fire at the start of the next tick). However, for a deadline timer, the TCP timer will always fire 1000us after you set the timer. -- John Baldwin
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