From: Thomas Graf <tgraf@suug.ch>
To: Nicolas DICHTEL <nicolas.dichtel@6wind.com>
Cc: netdev@oss.sgi.com, linux-net@vger.kernel.org
Subject: Re: Question about QOS
Date: Tue, 26 Apr 2005 14:59:55 +0200 [thread overview]
Message-ID: <20050426125955.GT577@postel.suug.ch> (raw)
In-Reply-To: <426E06F1.9000105@6wind.com>
* Nicolas DICHTEL <426E06F1.9000105@6wind.com> 2005-04-26 11:16
> I set CONFIG_NET_SCH_CLK_GETTIMEOFDAY in my kernel. The macro
> PSCHED_TDIFF_SAFE calculates
> the difference between two timestamps and uses the function
> psched_tod_diff() to do this.
> If the clock is readjusted (due to ntp for example), this function can
> return a negative number
> (if bound > 1000000) and then the flow is blocked by the kernel. Am I
> right ?
do_gettimeofday takes care of ntp adjustments so we _should_ be safe,
however, it might be wise to enforce a range of 0..bound instead of
INT_MIN..bound because qdiscs like red are relying on this. Assuming
we have a delta of -4 seconds and return -4e6 red will horribly
crash when acccessing the array with idle_time>>cell_log.
next prev parent reply other threads:[~2005-04-26 12:59 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-04-26 9:16 Question about QOS Nicolas DICHTEL
2005-04-26 12:59 ` Thomas Graf [this message]
2005-04-26 14:57 ` Nicolas DICHTEL
2005-04-26 19:14 ` Thomas Graf
2005-04-27 7:44 ` Nicolas DICHTEL
2005-04-27 11:42 ` Thomas Graf
2005-04-28 19:14 ` David S. Miller
2005-04-29 12:16 ` Patrick McHardy
2005-04-29 12:39 ` Thomas Graf
2005-05-03 21:40 ` David S. Miller
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