From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932421AbbA0QQN (ORCPT ); Tue, 27 Jan 2015 11:16:13 -0500 Received: from smtprelay0164.hostedemail.com ([216.40.44.164]:48428 "EHLO smtprelay.hostedemail.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755395AbbA0QQK (ORCPT ); Tue, 27 Jan 2015 11:16:10 -0500 X-Session-Marker: 6E657665747340676F6F646D69732E6F7267 X-Spam-Summary: 2,0,0,,d41d8cd98f00b204,rostedt@goodmis.org,:::::,RULES_HIT:41:355:379:541:599:800:960:973:988:989:1260:1277:1311:1313:1314:1345:1359:1431:1437:1515:1516:1518:1534:1543:1593:1594:1711:1730:1747:1777:1792:2393:2553:2559:2562:2693:2912:3138:3139:3140:3141:3142:3355:3622:3865:3866:3867:3868:3870:3871:3873:3874:4605:5007:6119:6261:7514:7875:10004:10400:10848:10967:11026:11232:11473:11658:11914:12043:12050:12296:12438:12517:12519:12555:12740:21080,0,RBL:none,CacheIP:none,Bayesian:0.5,0.5,0.5,Netcheck:none,DomainCache:0,MSF:not bulk,SPF:fn,MSBL:0,DNSBL:none,Custom_rules:0:0:0 X-HE-Tag: trade61_35728666d093a X-Filterd-Recvd-Size: 4021 Date: Tue, 27 Jan 2015 11:16:06 -0500 From: Steven Rostedt To: Tina Ruchandani Cc: Linux Kernel List , Ingo Molnar Subject: Re: [PATCH v3] trace: Use 64-bit timekeeping Message-ID: <20150127111606.195ac188@gandalf.local.home> In-Reply-To: <20150127155538.GA5132@tinar> References: <20150127155538.GA5132@tinar> X-Mailer: Claws Mail 3.11.1 (GTK+ 2.24.25; x86_64-pc-linux-gnu) 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 On Tue, 27 Jan 2015 21:25:38 +0530 Tina Ruchandani wrote: > The ring_buffer_producer uses 'struct timeval' to measure > its start and end times. 'struct timeval' on 32-bit systems > will have its tv_sec value overflow in year 2038 and beyond. > This patch replaces struct timeval with 'ktime_t' which uses > 64-bit representation for seconds Doesn't ktime_t actually use 64-bit representation for nanoseconds? > > Suggested-by: Arnd Bergmann > Signed-off-by: Tina Ruchandani > --- > Changes in v3: > - Use a more efficient way to compute condition for exiting > loop. > - Fix variable naming - all caps is only for macros. > Changes in v2: > - Use ktime_t instead of timespec64 for efficiency reasons. > --- > kernel/trace/ring_buffer_benchmark.c | 17 ++++++++--------- > 1 file changed, 8 insertions(+), 9 deletions(-) > > diff --git a/kernel/trace/ring_buffer_benchmark.c b/kernel/trace/ring_buffer_benchmark.c > index 3f9e328..0a50abb 100644 > --- a/kernel/trace/ring_buffer_benchmark.c > +++ b/kernel/trace/ring_buffer_benchmark.c > @@ -7,7 +7,7 @@ > #include > #include > #include > -#include > +#include > #include > > struct rb_page { > @@ -212,8 +212,7 @@ static void ring_buffer_consumer(void) > > static void ring_buffer_producer(void) > { > - struct timeval start_tv; > - struct timeval end_tv; > + ktime_t start_time, end_time, timeout; > unsigned long long time; > unsigned long long entries; > unsigned long long overruns; > @@ -227,7 +226,9 @@ static void ring_buffer_producer(void) > * make the system stall) > */ > trace_printk("Starting ring buffer hammer\n"); > - do_gettimeofday(&start_tv); > + start_time = ktime_get(); > + timeout = ktime_add_ns(start_time, > + ((long long) RUN_TIME) * NSEC_PER_SEC); Instead of the (long long) typecast, could you define RUN_TIME as 10ULL. Makes the code a bit cleaner, and we can put that on one line. Rest looks fine. -- Steve > do { > struct ring_buffer_event *event; > int *entry; > @@ -244,7 +245,7 @@ static void ring_buffer_producer(void) > ring_buffer_unlock_commit(buffer, event); > } > } > - do_gettimeofday(&end_tv); > + end_time = ktime_get(); > > cnt++; > if (consumer && !(cnt % wakeup_interval)) > @@ -264,7 +265,7 @@ static void ring_buffer_producer(void) > cond_resched(); > #endif > > - } while (end_tv.tv_sec < (start_tv.tv_sec + RUN_TIME) && !kill_test); > + } while (ktime_before(end_time, timeout) && !kill_test); > trace_printk("End ring buffer hammer\n"); > > if (consumer) { > @@ -280,9 +281,7 @@ static void ring_buffer_producer(void) > wait_for_completion(&read_done); > } > > - time = end_tv.tv_sec - start_tv.tv_sec; > - time *= USEC_PER_SEC; > - time += (long long)((long)end_tv.tv_usec - (long)start_tv.tv_usec); > + time = ktime_us_delta(end_time, start_time); > > entries = ring_buffer_entries(buffer); > overruns = ring_buffer_overruns(buffer);