From: Eddie Kohler <kohler@cs.ucla.edu>
To: dccp@vger.kernel.org
Subject: Re: [RFC] dccp ccid-3: High-res or low-res timers?
Date: Mon, 17 Nov 2008 19:27:29 +0000 [thread overview]
Message-ID: <4921C5A1.5030609@cs.ucla.edu> (raw)
In-Reply-To: <20081115105042.GA7798@gerrit.erg.abdn.ac.uk>
Gerrit Renker wrote:
> I would appreciate some advice and insights regarding the use of
> high-resolution timers within a transport protocol, specifically
> DCCP with CCID-3 (RFC 5348).
>
> ...
>
> Summing up, I have doubts that basing CCID-3 will bring advantages and
> would much rather go the other way and (consistently) use lower resolution.
>
> Thoughts?
I agree. If one way must be chosen, then choose lower resolution timers.
The biggest potential problem with lower-resolution timers is that a sender's
rate might be limited, not by network characteristics, but by timer
resolution. But DCCP allows a fair amount of burstiness already. And there
may be ways to avoid rate limitation in common cases without resorting to
hrtimers. For example, a sending application could use a mixture of
non-blocking system calls, allowing the sending application to "poke" the DCCP
implementation on every scheduling.
At any rate, it seems worth trying.
Eddie
WARNING: multiple messages have this Message-ID (diff)
From: Eddie Kohler <kohler@cs.ucla.edu>
To: Gerrit Renker <gerrit@erg.abdn.ac.uk>,
Leandro Sales <leandroal@gmail.com>,
Arnaldo Carvalho de Melo <acme@redhat.com>,
ian.mcdonald@jandi.co.nz, DCCP Mailing List <dccp@vger.kernel.o
Subject: Re: [RFC] dccp ccid-3: High-res or low-res timers?
Date: Mon, 17 Nov 2008 11:27:29 -0800 [thread overview]
Message-ID: <4921C5A1.5030609@cs.ucla.edu> (raw)
In-Reply-To: <20081115105042.GA7798@gerrit.erg.abdn.ac.uk>
Gerrit Renker wrote:
> I would appreciate some advice and insights regarding the use of
> high-resolution timers within a transport protocol, specifically
> DCCP with CCID-3 (RFC 5348).
>
> ...
>
> Summing up, I have doubts that basing CCID-3 will bring advantages and
> would much rather go the other way and (consistently) use lower resolution.
>
> Thoughts?
I agree. If one way must be chosen, then choose lower resolution timers.
The biggest potential problem with lower-resolution timers is that a sender's
rate might be limited, not by network characteristics, but by timer
resolution. But DCCP allows a fair amount of burstiness already. And there
may be ways to avoid rate limitation in common cases without resorting to
hrtimers. For example, a sending application could use a mixture of
non-blocking system calls, allowing the sending application to "poke" the DCCP
implementation on every scheduling.
At any rate, it seems worth trying.
Eddie
next prev parent reply other threads:[~2008-11-17 19:27 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-09-29 18:33 Protocol not attached Leandro Sales
2008-09-29 18:37 ` Arnaldo Carvalho de Melo
2008-09-30 18:32 ` Leandro Sales
2008-09-30 19:16 ` Arnaldo Carvalho de Melo
2008-09-30 21:24 ` Leandro Sales
2008-09-30 22:11 ` Arnaldo Carvalho de Melo
2008-10-01 18:27 ` Leandro Sales
2008-10-01 19:18 ` Leandro Sales
2008-10-01 19:37 ` Arnaldo Carvalho de Melo
2008-10-01 19:43 ` Leandro Sales
2008-10-01 21:38 ` Leandro Sales
2008-10-01 22:20 ` Ian McDonald
2008-10-02 4:47 ` Gerrit Renker
2008-10-03 5:44 ` Leandro Sales
2008-10-03 13:24 ` Arnaldo Carvalho de Melo
2008-10-03 14:18 ` Arnaldo Carvalho de Melo
2008-10-11 7:35 ` Gerrit Renker
2008-10-11 17:28 ` Leandro Sales
2008-10-13 14:51 ` Gerrit Renker
2008-10-16 21:09 ` Leandro Sales
2008-10-17 6:06 ` Gerrit Renker
2008-10-18 11:06 ` Gerrit Renker
2008-10-20 13:13 ` Arnaldo Carvalho de Melo
2008-10-21 14:19 ` Leandro Sales
2008-10-21 14:32 ` Arnaldo Carvalho de Melo
2008-10-21 18:08 ` Leandro Sales
2008-10-22 1:37 ` Leandro Sales
2008-10-22 1:37 ` Leandro Sales
2008-10-22 11:38 ` Arnaldo Carvalho de Melo
2008-10-22 13:30 ` Leandro Sales
2008-10-22 15:55 ` Gerrit Renker
2008-10-22 19:27 ` Leandro Sales
2008-10-23 5:18 ` gerrit
2008-11-06 13:38 ` Leandro Sales
2008-11-06 15:20 ` Gerrit Renker
2008-11-06 15:38 ` Arnaldo Carvalho de Melo
2008-11-06 17:46 ` Leandro Sales
2008-11-06 18:04 ` Leandro Sales
2008-11-06 18:17 ` Leandro Sales
2008-11-06 22:05 ` Leandro Sales
2008-11-08 8:50 ` Gerrit Renker
2008-11-15 10:50 ` [RFC] dccp ccid-3: High-res or low-res timers? Gerrit Renker
2008-11-15 10:50 ` Gerrit Renker
2008-11-16 8:14 ` Ian McDonald
2008-11-16 8:14 ` Ian McDonald
2008-11-17 6:48 ` David Miller
2008-11-17 6:48 ` David Miller
2008-11-17 19:27 ` Eddie Kohler [this message]
2008-11-17 19:27 ` Eddie Kohler
2008-11-17 21:16 ` [dccp] [RFC] dccp ccid-3: High-res or low-res timers? <cross Gorry Fairhurst
2008-11-17 21:16 ` [RFC] dccp ccid-3: High-res or low-res timers? <cross post> Gorry Fairhurst
2008-11-18 5:07 ` [RFC] dccp ccid-3: High-res or low-res timers? Gerrit Renker
2008-11-18 5:07 ` Gerrit Renker
2008-11-18 6:14 ` Gerrit Renker
2008-11-18 6:14 ` Gerrit Renker
2008-11-18 17:41 ` Ian McDonald
2008-11-18 17:41 ` Ian McDonald
2008-11-20 6:24 ` Gerrit Renker
2008-11-20 6:24 ` Gerrit Renker
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