From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758880AbYDRVyA (ORCPT ); Fri, 18 Apr 2008 17:54:00 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751926AbYDRVxx (ORCPT ); Fri, 18 Apr 2008 17:53:53 -0400 Received: from netops-testserver-3-out.sgi.com ([192.48.171.28]:46315 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1751354AbYDRVxw (ORCPT ); Fri, 18 Apr 2008 17:53:52 -0400 From: Jonathan Lim Message-Id: <200804182154.m3ILsUAO097324@sabah.engr.sgi.com> Subject: Re: [PATCH] Provide u64 version of jiffies_to_usecs() in kernel/tsacct.c To: linux-kernel@vger.kernel.org Date: Fri, 18 Apr 2008 14:54:30 -0700 (PDT) Cc: akpm@linux-foundation.org, randy.dunlap@oracle.com, zippel@linux-m68k.org, tglx@linutronix.de In-Reply-To: from "jlim" at Feb 25, 2008 02:27:58 PM X-Mailer: ELM [version 2.5 PL6] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org It's possible that the values used in and returned from jiffies_to_usecs() are incorrect because of truncation when variables of type u64 are involved. So a function specific to that type is used instead. This version implements a correction to jiffies_64_to_usecs() based on feedback from Randy Dunlap and Roman Zippel. Diff'd against: linux/kernel/git/torvalds/linux-2.6.git Signed-off-by: Jonathan Lim --- a/include/linux/jiffies.h Thu Feb 14 18:04:14 PST 2008 +++ b/include/linux/jiffies.h Thu Feb 14 18:07:17 PST 2008 @@ -42,7 +42,7 @@ /* LATCH is used in the interval timer and ftape setup. */ #define LATCH ((CLOCK_TICK_RATE + HZ/2) / HZ) /* For divider */ -/* Suppose we want to devide two numbers NOM and DEN: NOM/DEN, then we can +/* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can * improve accuracy by shifting LSH bits, hence calculating: * (NOM << LSH) / DEN * This however means trouble for large NOM, because (NOM << LSH) may no @@ -204,7 +204,7 @@ extern unsigned long preset_lpj; * operator if the result is a long long AND at least one of the * operands is cast to long long (usually just prior to the "*" so as * not to confuse it into thinking it really has a 64-bit operand, - * which, buy the way, it can do, but it takes more code and at least 2 + * which, by the way, it can do, but it takes more code and at least 2 * mpys). * We also need to be aware that one second in nanoseconds is only a @@ -269,6 +269,7 @@ extern unsigned long preset_lpj; */ extern unsigned int jiffies_to_msecs(const unsigned long j); extern unsigned int jiffies_to_usecs(const unsigned long j); +extern u64 jiffies_64_to_usecs(const u64 j); extern unsigned long msecs_to_jiffies(const unsigned int m); extern unsigned long usecs_to_jiffies(const unsigned int u); extern unsigned long timespec_to_jiffies(const struct timespec *value); --- a/kernel/time.c Thu Feb 14 18:05:12 PST 2008 +++ b/kernel/time.c Fri Apr 18 14:44:54 PDT 2008 @@ -38,6 +38,7 @@ #include #include +#include #include "timeconst.h" @@ -267,6 +268,16 @@ unsigned int inline jiffies_to_usecs(con #endif } EXPORT_SYMBOL(jiffies_to_usecs); + +u64 jiffies_64_to_usecs(const u64 j) +{ +# if BITS_PER_LONG == 32 + return ((u64)HZ_TO_USEC_MUL32 * j) >> HZ_TO_USEC_SHR32; +# else + return div64_64(j*HZ_TO_USEC_NUM + HZ_TO_USEC_DEN-1, HZ_TO_USEC_DEN); +# endif +} +EXPORT_SYMBOL(jiffies_64_to_usecs); /** * timespec_trunc - Truncate timespec to a granularity --- a/kernel/tsacct.c Thu Feb 14 18:06:17 PST 2008 +++ b/kernel/tsacct.c Thu Feb 14 18:08:47 PST 2008 @@ -85,8 +85,8 @@ void xacct_add_tsk(struct taskstats *sta struct mm_struct *mm; /* convert pages-jiffies to Mbyte-usec */ - stats->coremem = jiffies_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB; - stats->virtmem = jiffies_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB; + stats->coremem = jiffies_64_to_usecs(p->acct_rss_mem1) * PAGE_SIZE / MB; + stats->virtmem = jiffies_64_to_usecs(p->acct_vm_mem1) * PAGE_SIZE / MB; mm = get_task_mm(p); if (mm) { /* adjust to KB unit */