From: "H. Peter Anvin" <hpa@zytor.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org,
a.p.zijlstra@chello.nl, torvalds@linux-foundation.org,
zheng.z.yan@intel.com, tglx@linutronix.de,
linux-tip-commits@vger.kernel.org
Subject: Re: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support
Date: Thu, 21 Jun 2012 16:10:23 -0700 [thread overview]
Message-ID: <4FE3A9DF.20303@zytor.com> (raw)
In-Reply-To: <20120621155159.239aa972.akpm@linux-foundation.org>
On 06/21/2012 03:51 PM, Andrew Morton wrote:
>
> What *is* significant is the effect of a signedness change upon
> arithmetic, conversions, warnings, etc. And whether such a change
> might actually introduce bugs.
>
>
> Back away and ask the broader questions: why did ktime_t choose
> unsigned? Is time a signed concept? What is the right thing to do
> here, from a long-term design perspective?
Time is definitely a signed concept -- it has no beginning or end (well,
the Big Bang, but the ±110 Myr or so uncertainty of the exact timing of
the Big Bang makes it a horridly awkward choice for epoch.)
Now, for some users of time you can inherently guarantee there will
never be any references to time before a particular event, e.g. system
boot, in which case an unsigned number might make sense, but as a whole
I think using a signed type as time_t in nearly all Unix implementation
was The Right Thing.
-hpa
next prev parent reply other threads:[~2012-06-21 23:10 UTC|newest]
Thread overview: 74+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-15 6:31 [PATCH V6 0/13] perf: Intel uncore pmu counting support Yan, Zheng
2012-06-15 6:31 ` [PATCH V6 01/13] perf: Export perf_assign_events Yan, Zheng
2012-06-20 10:49 ` [tip:perf/core] perf: Export perf_assign_events() tip-bot for Yan, Zheng
2012-06-15 6:31 ` [PATCH V6 02/13] perf: Avoid race between cpu hotplug and installing event Yan, Zheng
2012-06-20 10:50 ` [tip:perf/core] " tip-bot for Yan, Zheng
2012-06-15 6:31 ` [PATCH V6 03/13] perf: Allow pmu to choose cpu on which to install event Yan, Zheng
2012-06-20 10:51 ` [tip:perf/core] perf: Allow the PMU driver to choose the CPU on which to install events tip-bot for Yan, Zheng
2012-06-15 6:31 ` [PATCH V6 04/13] perf: Introduce perf_pmu_migrate_context Yan, Zheng
2012-06-20 10:52 ` [tip:perf/core] perf: Introduce perf_pmu_migrate_context() tip-bot for Yan, Zheng
2012-06-15 6:31 ` [PATCH V6 05/13] perf: Generic intel uncore support Yan, Zheng
2012-06-20 10:54 ` [tip:perf/core] perf/x86: Add generic Intel uncore PMU support tip-bot for Yan, Zheng
2012-06-21 22:43 ` Andrew Morton
2012-06-21 22:46 ` Andrew Morton
2012-06-21 22:47 ` H. Peter Anvin
2012-06-21 22:51 ` Andrew Morton
2012-06-21 23:10 ` H. Peter Anvin [this message]
2012-06-21 23:15 ` Andrew Morton
2012-06-21 23:18 ` Andrew Morton
2012-06-21 23:22 ` H. Peter Anvin
2012-06-21 23:29 ` Andrew Morton
2012-06-22 8:05 ` Peter Zijlstra
2012-07-24 3:27 ` [PATCH V6 05/13] perf: Generic intel uncore support Stephane Eranian
2012-07-24 6:00 ` Yan, Zheng
2012-07-24 6:21 ` Stephane Eranian
2012-06-15 6:31 ` [PATCH V6 06/13] perf: Add Nehalem and Sandy Bridge " Yan, Zheng
2012-06-15 15:28 ` Peter Zijlstra
2012-06-15 16:31 ` Peter Zijlstra
2012-06-15 18:43 ` Andi Kleen
2012-06-15 17:18 ` Peter Zijlstra
2012-06-15 18:46 ` Stephane Eranian
2012-06-16 12:46 ` Peter Zijlstra
2012-06-16 12:52 ` Peter Zijlstra
2012-06-18 9:23 ` Stephane Eranian
2012-06-19 1:39 ` Yan, Zheng
2012-06-15 17:29 ` Peter Zijlstra
2012-06-15 18:47 ` Stephane Eranian
2012-06-16 12:46 ` Peter Zijlstra
2012-06-20 10:55 ` [tip:perf/core] perf/x86: Add Intel Nehalem and Sandy Bridge uncore PMU support tip-bot for Yan, Zheng
2012-06-15 6:31 ` [PATCH V6 07/13] perf: Generic pci uncore device support Yan, Zheng
2012-06-15 16:02 ` Peter Zijlstra
2012-06-18 3:06 ` Yan, Zheng
2012-06-18 7:43 ` Peter Zijlstra
2012-06-20 10:56 ` [tip:perf/core] perf: Add generic PCI uncore PMU " tip-bot for Yan, Zheng
2012-06-20 16:39 ` [PATCH] perf, x86: Fix section mismatch in uncore_pci_init() Robert Richter
2012-06-25 11:40 ` [tip:perf/core] perf/x86: Fix section mismatch in uncore_pci_init( ) tip-bot for Robert Richter
2012-08-13 17:10 ` [tip:perf/urgent] perf, x86: Fix uncore_types_exit section mismatch tip-bot for Borislav Petkov
2012-06-15 6:31 ` [PATCH V6 08/13] perf: Add Sandy Bridge-EP uncore support Yan, Zheng
2012-06-15 17:10 ` Peter Zijlstra
2012-06-18 1:47 ` Yan, Zheng
2012-06-18 7:42 ` Peter Zijlstra
2012-06-18 15:28 ` Stephane Eranian
2012-06-19 0:59 ` Yan, Zheng
2012-06-19 7:18 ` Stephane Eranian
2012-06-19 8:17 ` Yan, Zheng
2012-06-20 10:56 ` [tip:perf/core] perf/x86: Add Intel Nehalem and " tip-bot for Yan, Zheng
2012-07-22 19:37 ` [PATCH V6 08/13] perf: Add " Stephane Eranian
2012-06-15 6:31 ` [PATCH V6 09/13] perf, tool: Use data struct for arg passing in event parse function Yan, Zheng
2012-06-20 10:57 ` [tip:perf/core] perf/tool: " tip-bot for Jiri Olsa
2012-06-15 6:31 ` [PATCH V6 10/13] perf, tool: Make the event parser reentrantable Yan, Zheng
2012-06-20 10:58 ` [tip:perf/core] perf/tool: Make the event parser re-entrant tip-bot for Zheng Yan
2012-06-15 6:31 ` [PATCH V6 11/13] perf, tool: Add support to reuse event grammar to parse out terms Yan, Zheng
2012-06-20 10:59 ` [tip:perf/core] perf/tool: " tip-bot for Jiri Olsa
2012-06-15 6:31 ` [PATCH V6 12/13] perf, tool: Add pmu event alias support Yan, Zheng
2012-06-20 11:00 ` [tip:perf/core] perf/tool: Add PMU " tip-bot for Zheng Yan
2012-06-15 6:31 ` [PATCH V6 13/13] perf, tool: Add automated test for pure terms parsing Yan, Zheng
2012-06-20 11:01 ` [tip:perf/core] perf/tool: " tip-bot for Jiri Olsa
2012-06-20 16:01 ` [PATCH V6 0/13] perf: Intel uncore pmu counting support Peter Zijlstra
2012-06-21 2:34 ` Yan, Zheng
2012-06-21 8:10 ` Stephane Eranian
2012-06-21 8:43 ` Yan, Zheng
2012-06-21 9:13 ` Stephane Eranian
2012-06-21 11:40 ` Peter Zijlstra
2012-06-21 11:48 ` Stephane Eranian
2012-06-21 13:08 ` Yan, Zheng
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