From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756185AbYAHBDk (ORCPT ); Mon, 7 Jan 2008 20:03:40 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754630AbYAHBDc (ORCPT ); Mon, 7 Jan 2008 20:03:32 -0500 Received: from relay1.sgi.com ([192.48.171.29]:56274 "EHLO relay.sgi.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752758AbYAHBDc (ORCPT ); Mon, 7 Jan 2008 20:03:32 -0500 From: Jonathan Lim Message-Id: <200801080104.m08148Mo063726@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: Mon, 7 Jan 2008 17:04:08 -0800 (PST) Cc: hpa@zytor.com, akpm@linux-foundation.org, jlan@sgi.com In-Reply-To: from "jlim" at Dec 28, 2007 01:26:07 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. Updated from previous submission with feedback from Peter Anvin. Diff'd against: linux/kernel/git/torvalds/linux-2.6.git Signed-off-by: Jonathan Lim --- a/include/linux/jiffies.h 2008-01-07 16:09:17.737040981 -0800 +++ b/include/linux/jiffies.h 2008-01-07 16:09:17.693033003 -0800 @@ -36,7 +36,7 @@ /* 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 @@ -198,7 +198,7 @@ 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 @@ -263,6 +263,7 @@ 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 2008-01-07 16:09:17.841059839 -0800 +++ b/kernel/time.c 2008-01-07 16:09:17.825056938 -0800 @@ -267,6 +267,12 @@ unsigned int inline jiffies_to_usecs(con } EXPORT_SYMBOL(jiffies_to_usecs); +u64 inline jiffies_64_to_usecs(const u64 j) +{ + return (j*HZ_TO_USEC_NUM + HZ_TO_USEC_DEN-1) / HZ_TO_USEC_DEN; +} +EXPORT_SYMBOL(jiffies_64_to_usecs); + /** * timespec_trunc - Truncate timespec to a granularity * @t: Timespec --- a/kernel/tsacct.c 2008-01-07 16:09:17.833058389 -0800 +++ b/kernel/tsacct.c 2008-01-07 16:09:17.793051136 -0800 @@ -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 */