| To: | Andrew Morton <akpm@xxxxxxxx> |
|---|---|
| Subject: | Re: MSEC_TO_JIFFIES is messed up... |
| From: | William Lee Irwin III <wli@xxxxxxxxxxxxxx> |
| Date: | Wed, 12 May 2004 13:59:15 -0700 |
| Cc: | mingo@xxxxxxx, davidel@xxxxxxxxxxxxxxx, jgarzik@xxxxxxxxx, greg@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx |
| In-reply-to: | <20040512134718.7e55cceb.akpm@osdl.org> |
| Mail-followup-to: | William Lee Irwin III <wli@xxxxxxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxx>, mingo@xxxxxxx, davidel@xxxxxxxxxxxxxxx, jgarzik@xxxxxxxxx, greg@xxxxxxxxx, linux-kernel@xxxxxxxxxxxxxxx, netdev@xxxxxxxxxxx |
| References: | <20040512020700.6f6aa61f.akpm@osdl.org> <20040512181903.GG13421@kroah.com> <40A26FFA.4030701@pobox.com> <20040512193349.GA14936@elte.hu> <Pine.LNX.4.58.0405121247011.11950@bigblue.dev.mdolabs.com> <20040512200305.GA16078@elte.hu> <20040512132050.6eae6905.akpm@osdl.org> <20040512203829.GI1397@holomorphy.com> <20040512134718.7e55cceb.akpm@osdl.org> |
| Sender: | netdev-bounce@xxxxxxxxxxx |
| User-agent: | Mutt/1.5.5.1+cvs20040105i |
William Lee Irwin III <wli@xxxxxxxxxxxxxx> wrote: >> How about this? >> #if HZ <= 1000 && !(1000 % HZ) >> #define MSEC_TO_JIFFIES(m) ((1000/HZ)*(m)) >> #define JIFFIES_TO_MSEC(j) ((j)/(1000/HZ)) >> #elif HZ > 1000 && !(HZ % 1000) >> #define MSEC_TO_JIFFIES(m) ((m)/(HZ/1000)) >> #define JIFFIES_TO_MSEC(j) ((HZ/1000)*(j)) >> #else >> #define MSEC_TO_JIFFIES(m) ((HZ*(m) + 999)/1000) >> #define JIFFIES_TO_MSEC(j) ((1000*(j) + HZ - 1)/HZ) >> #endif On Wed, May 12, 2004 at 01:47:18PM -0700, Andrew Morton wrote: > You promise it's correct and generates good code? Yes. Changelog: Optimize the cases where HZ is a divisor of 1000 or vice-versa in JIFFIES_TO_MSEC() and MSEC_TO_JIFFIES() by allowing the nonvanishing(!) integral ratios to appear as a parenthesized expressions eligible for constant folding optimizations. I'll resend the #ifdef logic against Ingo's latest, which is orthogonal. -- wli |
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