From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760126AbYBSV0m (ORCPT ); Tue, 19 Feb 2008 16:26:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753388AbYBSV0e (ORCPT ); Tue, 19 Feb 2008 16:26:34 -0500 Received: from agminet01.oracle.com ([141.146.126.228]:40837 "EHLO agminet01.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753190AbYBSV0d (ORCPT ); Tue, 19 Feb 2008 16:26:33 -0500 Date: Tue, 19 Feb 2008 13:25:25 -0800 From: Randy Dunlap To: Jonathan Lim Cc: linux-kernel@vger.kernel.org, akpm@linux-foundation.org Subject: Re: [PATCH] Provide u64 version of jiffies_to_usecs() in kernel/tsacct.c Message-Id: <20080219132525.a81e8264.randy.dunlap@oracle.com> In-Reply-To: <200802192052.m1JKqk9K002857@sabah.engr.sgi.com> References: <200802192052.m1JKqk9K002857@sabah.engr.sgi.com> Organization: Oracle Linux Eng. X-Mailer: Sylpheed 2.4.7 (GTK+ 2.8.10; x86_64-unknown-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Brightmail-Tracker: AAAAAQAAAAI= X-Brightmail-Tracker: AAAAAQAAAAI= X-Whitelist: TRUE X-Whitelist: TRUE Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 19 Feb 2008 12:52:46 -0800 (PST) Jonathan Lim wrote: > 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. > > 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 Tue Feb 19 12:44:03 PST 2008 > @@ -268,6 +268,14 @@ unsigned int inline jiffies_to_usecs(con > } > EXPORT_SYMBOL(jiffies_to_usecs); > > +u64 inline jiffies_64_to_usecs(const u64 j) > +{ > + u64 tmp = j*HZ_TO_USEC_NUM + HZ_TO_USEC_DEN-1; > + do_div(tmp, HZ_TO_USEC_DEN); do_div() is: * The semantics of do_div() are: * * uint32_t do_div(uint64_t *n, uint32_t base) Maybe you want div64_64(). > + return tmp; > +} > +EXPORT_SYMBOL(jiffies_64_to_usecs); > + > /** > * timespec_trunc - Truncate timespec to a granularity > * @t: Timespec > --- 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 */ > -- --- ~Randy