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Message-ID: <52A5CD19.1020207@intel.com>
Date: Mon, 09 Dec 2013 16:00:57 +0200
From: Adrian Hunter <adrian.hunter@...el.com>
To: Jiri Olsa <jolsa@...hat.com>
CC: Arnaldo Carvalho de Melo <acme@...stprotocols.net>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
David Ahern <dsahern@...il.com>,
Frederic Weisbecker <fweisbec@...il.com>,
Mike Galbraith <efault@....de>,
Namhyung Kim <namhyung@...il.com>,
Paul Mackerras <paulus@...ba.org>,
Stephane Eranian <eranian@...gle.com>
Subject: Re: [PATCH 2/4] perf tools: Fix max mmap_pages
On 09/12/13 15:35, Jiri Olsa wrote:
> On Mon, Dec 09, 2013 at 03:18:38PM +0200, Adrian Hunter wrote:
>> 'SIZE_MAX / page_size' is an upper limit for
>> the maximum number of mmap pages, not a lower
>> limit. Change the condition accordingly.
>>
>> Signed-off-by: Adrian Hunter <adrian.hunter@...el.com>
>> ---
>> tools/perf/util/evlist.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
>> index 4d0945c..98ec96b 100644
>> --- a/tools/perf/util/evlist.c
>> +++ b/tools/perf/util/evlist.c
>> @@ -754,7 +754,7 @@ int perf_evlist__parse_mmap_pages(const struct option *opt, const char *str,
>> unsigned long max = UINT_MAX;
>> long pages;
>>
>> - if (max < SIZE_MAX / page_size)
>> + if (max > SIZE_MAX / page_size)
>> max = SIZE_MAX / page_size;
>
> I agree with the change.. but it looks like the check
> is superfluos, maybe we want to define max as:
>
> unsigned long max = SIZE_MAX / page_size
I think it is OK because mmap_pages (in struct perf_record_opts) is an
unsigned int i.e.
max = MIN(UINT_MAX, SIZE_MAX / 4096)
c.f.
32-bit 64-bit
UINT_MAX 2^32 - 1 2^32 - 1
SIZE_MAX 2^32 - 1 2^64 - 1
SIZE_MAX / 4096 2^20 - 1 2^52 - 1
So on 32-bit the max is SIZE_MAX / 4096 but on
64-bit the max is UINT_MAX
>
> ?
>
> jirka
>>
>> pages = parse_pages_arg(str, 1, max);
>> --
>> 1.7.11.7
>>
>
>
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