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Date: Thu, 06 Dec 2007 16:22:05 -0800 From: Jeremy Fitzhardinge <jeremy@...p.org> To: Adrian Bunk <bunk@...nel.org> CC: "H. Peter Anvin" <hpa@...or.com>, Andrew Morton <akpm@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Alan Cox <alan@...rguk.ukuu.org.uk> Subject: Re: [PATCH] Avoid overflows in kernel/time.c 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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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