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From: Sonny Rao <sonnyrao@chromium.org>
To: Robert Foss <robert.foss@collabora.com>
Cc: Michal Hocko <mhocko@kernel.org>,
	Jonathan Corbet <corbet@lwn.net>,
	Andrew Morton <akpm@linux-foundation.org>,
	Vlastimil Babka <vbabka@suse.cz>, Hugh Dickins <hughd@google.com>,
	Konstantin Khlebnikov <koct9i@gmail.com>,
	Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>,
	"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
	John Stultz <john.stultz@linaro.org>,
	Minchan Kim <minchan@kernel.org>,
	ross.zwisler@linux.intel.com, jmarchan@redhat.com,
	Johannes Weiner <hannes@cmpxchg.org>,
	Kees Cook <keescook@chromium.org>,
	oleg@redhat.com, Al Viro <viro@zeniv.linux.org.uk>,
	Mateusz Guzik <mguzik@redhat.com>,
	Janis Danisevskis <jdanis@google.com>,
	calvinowens@fb.com, Alexey Dobriyan <adobriyan@gmail.com>,
	ebiederm@xmission.com, Seth Forshee <seth.forshee@canonical.com>,
	Djalal Harouni <tixxdz@gmail.com>,
	linux-doc@vger.kernel.org,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	Ben Zhang <benzh@chromium.org>, Bryan Freed <bfreed@chromium.org>,
	Filipe Brandenburger <filbranden@chromium.org>,
	Jann Horn <jann@thejh.net>,
	linux-api@vger.kernel.org,
	Jacek Anaszewski <j.anaszewski@samsung.com>
Subject: Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps
Date: Mon, 19 Sep 2016 17:29:56 -0700	[thread overview]
Message-ID: <CAPz6YkWWUJLPauKZ6yQuVfZY0etNM+LSU4Z0TW+Lj8xHPnkcuQ@mail.gmail.com> (raw)
In-Reply-To: <2bfaecf2-bf68-48b2-8a88-6e8997c229db@collabora.com>

On Mon, Sep 19, 2016 at 5:27 PM, Robert Foss <robert.foss@collabora.com> wrote:
>
>
> On 2016-09-19 03:32 PM, Michal Hocko wrote:
>>
>> On Mon 19-09-16 11:16:31, Robert Foss wrote:
>>>
>>> On 2016-09-14 05:12 AM, Michal Hocko wrote:
>>>>
>>>> On Tue 13-09-16 13:27:39, Sonny Rao wrote:
>>
>> [...]
>>>>>
>>>>> Given that smaps
>>>>> doesn't provide this in a straightforward way, what do you think is
>>>>> the right way to provide this information?
>>>>
>>>>
>>>> I would be tempted to sneak it into /proc/<pid>/statm because that looks
>>>> like a proper place but getting this information is not for free
>>>> performance wise so I am not really sure something that relies on this
>>>> file would see unexpected stalls. Maybe this could be worked around by
>>>> some caching... I would suggest to check who is actually using this file
>>>> (top/ps etc...)
>>>
>>>
>>> What would this caching look like? Can any information be re-used between
>>> vma walks?
>>
>>
>> yes basically return the same value if called within HZ or something
>> similar. But that assumes that statm latency really matters and it is
>> called often enough.
>
>
> Any single application querying more often than HZ, would presumably do so
> for accuracy reasons.
> However for multiple applications that combined query more often than HZ,
> this would most definitely be halpful in terms of performance.
>
> @Sonny, does chromiumos fall into the first or second category?

It's a single application -- and it definitely doesn't query at HZ --
especially given how long it takes to gather the data :-)

WARNING: multiple messages have this Message-ID (diff)
From: Sonny Rao <sonnyrao-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
To: Robert Foss <robert.foss-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>
Cc: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	Jonathan Corbet <corbet-T1hC0tSOHrs@public.gmane.org>,
	Andrew Morton
	<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Vlastimil Babka <vbabka-AlSwsSmVLrQ@public.gmane.org>,
	Hugh Dickins <hughd-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	Konstantin Khlebnikov
	<koct9i-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	Naoya Horiguchi
	<n-horiguchi-PaJj6Psr51x8UrSeD/g0lQ@public.gmane.org>,
	"Kirill A. Shutemov"
	<kirill.shutemov-VuQAYsv1563Yd54FQh9/CA@public.gmane.org>,
	John Stultz <john.stultz-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>,
	Minchan Kim <minchan-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	ross.zwisler-VuQAYsv1563Yd54FQh9/CA@public.gmane.org,
	jmarchan-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>,
	Kees Cook <keescook-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
	oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org,
	Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>,
	Mateusz Guzik <mguzik-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
	Janis Danisevskis
	<jdanis-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>,
	calvinowens-b10kYP2dOMg@public.gmane.org,
	Alexey Dobriyan
	<adobriyan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
	ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org,
	Seth Forshee
	<seth.forshee-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>
Subject: Re: [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps
Date: Mon, 19 Sep 2016 17:29:56 -0700	[thread overview]
Message-ID: <CAPz6YkWWUJLPauKZ6yQuVfZY0etNM+LSU4Z0TW+Lj8xHPnkcuQ@mail.gmail.com> (raw)
In-Reply-To: <2bfaecf2-bf68-48b2-8a88-6e8997c229db-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org>

On Mon, Sep 19, 2016 at 5:27 PM, Robert Foss <robert.foss-ZGY8ohtN/8qB+jHODAdFcQ@public.gmane.org> wrote:
>
>
> On 2016-09-19 03:32 PM, Michal Hocko wrote:
>>
>> On Mon 19-09-16 11:16:31, Robert Foss wrote:
>>>
>>> On 2016-09-14 05:12 AM, Michal Hocko wrote:
>>>>
>>>> On Tue 13-09-16 13:27:39, Sonny Rao wrote:
>>
>> [...]
>>>>>
>>>>> Given that smaps
>>>>> doesn't provide this in a straightforward way, what do you think is
>>>>> the right way to provide this information?
>>>>
>>>>
>>>> I would be tempted to sneak it into /proc/<pid>/statm because that looks
>>>> like a proper place but getting this information is not for free
>>>> performance wise so I am not really sure something that relies on this
>>>> file would see unexpected stalls. Maybe this could be worked around by
>>>> some caching... I would suggest to check who is actually using this file
>>>> (top/ps etc...)
>>>
>>>
>>> What would this caching look like? Can any information be re-used between
>>> vma walks?
>>
>>
>> yes basically return the same value if called within HZ or something
>> similar. But that assumes that statm latency really matters and it is
>> called often enough.
>
>
> Any single application querying more often than HZ, would presumably do so
> for accuracy reasons.
> However for multiple applications that combined query more often than HZ,
> this would most definitely be halpful in terms of performance.
>
> @Sonny, does chromiumos fall into the first or second category?

It's a single application -- and it definitely doesn't query at HZ --
especially given how long it takes to gather the data :-)

  reply	other threads:[~2016-09-20  0:37 UTC|newest]

Thread overview: 43+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-09-05 20:14 [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps robert.foss
2016-09-05 20:14 ` robert.foss
2016-09-05 20:14 ` [PATCH v5 1/3] " robert.foss
2016-09-05 20:14   ` robert.foss
2016-09-07 12:58   ` Oleg Nesterov
2016-09-07 12:58     ` Oleg Nesterov
2016-09-12 22:12     ` Robert Foss
2016-09-12 22:12       ` Robert Foss
2016-09-05 20:14 ` [PATCH v5 2/3] Documentation/filesystems: Fixed typo robert.foss
2016-09-05 20:14   ` robert.foss-ZGY8ohtN/8qB+jHODAdFcQ
2016-09-07 23:22   ` Kees Cook
2016-09-07 23:22     ` Kees Cook
2016-09-08  0:22     ` Robert Foss
2016-09-08  0:22       ` Robert Foss
2016-09-08  6:23       ` Jonathan Corbet
2016-09-08  6:23         ` Jonathan Corbet
2016-09-05 20:14 ` [PATCH v5 3/3] Documentation/filesystems: Added /proc/PID/totmaps documentation robert.foss
2016-09-05 20:14   ` robert.foss
2016-09-12 12:02 ` [PATCH v5 0/3] mm, proc: Implement /proc/<pid>/totmaps Michal Hocko
2016-09-12 15:31   ` Sonny Rao
2016-09-12 15:31     ` Sonny Rao
2016-09-12 17:15     ` Michal Hocko
2016-09-12 17:15       ` Michal Hocko
2016-09-12 17:28       ` Sonny Rao
2016-09-12 17:28         ` Sonny Rao
2016-09-13  7:12         ` Michal Hocko
2016-09-13  7:12           ` Michal Hocko
2016-09-13 20:27           ` Sonny Rao
2016-09-13 20:27             ` Sonny Rao
2016-09-14  9:12             ` Michal Hocko
2016-09-14  9:12               ` Michal Hocko
2016-09-19 15:16               ` Robert Foss
2016-09-19 15:16                 ` Robert Foss
2016-09-19 19:32                 ` Michal Hocko
2016-09-19 19:32                   ` Michal Hocko
     [not found]                   ` <20160919194001.GE2903@pc.thejh.net>
     [not found]                     ` <20160919195109.GB28639@dhcp22.suse.cz>
2016-09-19 19:56                       ` Jann Horn
2016-09-19 19:56                         ` Jann Horn
2016-09-19 20:15                         ` Sonny Rao
2016-09-19 20:15                           ` Sonny Rao
2016-09-20  0:27                   ` Robert Foss
2016-09-20  0:27                     ` Robert Foss
2016-09-20  0:29                     ` Sonny Rao [this message]
2016-09-20  0:29                       ` Sonny Rao

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