From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Adrian Bunk <bunk@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
Andrew Morton <akpm@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Alan Cox <alan@lxorguk.ukuu.org.uk>
Subject: Re: [PATCH] Avoid overflows in kernel/time.c
Date: Thu, 06 Dec 2007 16:22:05 -0800 [thread overview]
Message-ID: <4758922D.7010006@goop.org> (raw)
In-Reply-To: <20071201003333.GR29463@stusta.de>
Adrian Bunk wrote:
> On Thu, Nov 29, 2007 at 04:19:51PM -0800, H. Peter Anvin wrote:
>
>> When the conversion factor between jiffies and milli- or microseconds
>> is not a single multiply or divide, as for the case of HZ == 300, we
>> currently do a multiply followed by a divide. The intervening
>> result, however, is subject to overflows, especially since the
>> fraction is not simplified (for HZ == 300, we multiply by 300 and
>> divide by 1000).
>> ...
>> kernel/Makefile | 8 +++
>> kernel/time.c | 29 +++++++++---
>> kernel/timeconst.bc | 123 +++++++++++++++++++++++++++++++++++++++++++++++++++
>> 3 files changed, 152 insertions(+), 8 deletions(-)
>> create mode 100644 kernel/timeconst.bc
>> ...
>>
>
> I have read the hep text, but are the advantages of HZ == 300 really
> visible or was this more theoretical?
>
> In the latter case, we might remove the HZ == 300 choice instead.
>
300 is useful for video applications, since its a multiple of both 50
and 60Hz. Tickless may make this less relevent though.
J
next prev parent reply other threads:[~2007-12-07 0:22 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-11-30 0:19 [PATCH] Avoid overflows in kernel/time.c H. Peter Anvin
2007-11-30 1:54 ` Andrew Morton
2007-11-30 3:01 ` H. Peter Anvin
2007-11-30 3:27 ` [PATCH] Documentation/Changes -> Documentation/Requirements H. Peter Anvin
2007-11-30 3:32 ` [PATCH] Documentation/Changes -> Documentation/Requirements (resend without truncated comment text) H. Peter Anvin
2007-11-30 7:16 ` Jarek Poplawski
2007-11-30 17:40 ` H. Peter Anvin
2007-11-30 17:47 ` [PATCH] Documentation/Changes -> Documentation/Requirements H. Peter Anvin
2007-11-30 18:09 ` Robert P. J. Day
2007-11-30 18:20 ` H. Peter Anvin
2007-11-30 1:59 ` [PATCH] Avoid overflows in kernel/time.c Chris Snook
2007-11-30 3:04 ` H. Peter Anvin
2007-11-30 3:40 ` Arjan van de Ven
2007-11-30 3:54 ` H. Peter Anvin
2007-12-02 18:37 ` Pavel Machek
2007-12-03 14:53 ` Jan Engelhardt
2007-12-10 16:37 ` H. Peter Anvin
2007-12-01 0:33 ` Adrian Bunk
2007-12-01 4:19 ` H. Peter Anvin
2007-12-01 13:20 ` Alan Cox
2007-12-01 13:33 ` Alan Cox
2007-12-02 1:53 ` H. Peter Anvin
2007-12-07 0:22 ` Jeremy Fitzhardinge [this message]
2007-12-04 11:29 ` Andrew Morton
2007-12-10 16:46 ` H. Peter Anvin
2007-12-10 18:59 ` H. Peter Anvin
2007-12-10 22:04 ` Andrew Morton
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