From: Pekka Enberg <penberg@kernel.org>
To: KOSAKI Motohiro <kosaki.motohiro@gmail.com>
Cc: Anton Vorontsov <anton.vorontsov@linaro.org>,
Minchan Kim <minchan@kernel.org>,
Leonid Moiseichuk <leonid.moiseichuk@nokia.com>,
John Stultz <john.stultz@linaro.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
linaro-kernel@lists.linaro.org, patches@linaro.org,
kernel-team@android.com
Subject: Re: [PATCH 3/3] vmevent: Implement special low-memory attribute
Date: Tue, 8 May 2012 11:03:05 +0300 [thread overview]
Message-ID: <CAOJsxLGWtJy7q6ij_-tN8nVTr-OXpgdWVkXsOda8S9mJzo7n2w@mail.gmail.com> (raw)
In-Reply-To: <4FA8D046.7000808@gmail.com>
On Tue, May 8, 2012 at 10:50 AM, KOSAKI Motohiro
<kosaki.motohiro@gmail.com> wrote:
>>> 1) sample_period is brain damaged idea. If people ONLY need to
>>> sampling stastics, they
>>> only need to read /proc/vmstat periodically. just remove it and
>>> implement push notification.
>>> _IF_ someone need unfrequent level trigger, just use
>>> "usleep(timeout); read(vmevent_fd)"
>>> on userland code.
>>
>> That comes from a real-world requirement. See Leonid's email on the topic:
>>
>> https://lkml.org/lkml/2012/5/2/42
>
> I know, many embedded guys prefer such timer interval. I also have an
> experience
> similar logic when I was TV box developer. but I must disagree. Someone hope
> timer housekeeping complexity into kernel. but I haven't seen any
> justification.
Leonid?
>>> 6) Also vmevent_event must hide from userland.
>>
>> Why? That's part of the ABI.
>
> Ahhh, if so, I missed something. as far as I look, vmevent_fd() only depend
> on vmevent_config. which syscall depend on vmevent_evennt?
read(2). See tools/testing/vmevent/vmevent-test.c for an example how
the ABI is used.
>>> 7) vmevent_config::size must be removed. In 20th century, M$ API
>>> prefer to use this technique. But
>>> They dropped the way because a lot of application don't initialize
>>> size member and they can't use it for keeping upper compitibility.
>>
>> It's there to support forward/backward ABI compatibility like perf
>> does. I'm going to keep it for now but I'm open to dropping it when
>> the ABI is more mature.
>
> perf api is not intended to use from generic applications. then, I don't
> think it will make abi issue. tool/perf is sane, isn't it? but vmevent_fd()
> is generic api and we can't trust all userland guy have sane, unfortunately.
The perf ABI is being used by other projects as well. We don't
_depend_ on ->size being sane as much as use it to detect new features
in the future.
But anyway, we can consider dropping once the ABI is more stable.
> Hm. If you want vmevent makes depend on CONFIG_EMBEDDED, I have no reason to
> complain this feature. At that world, almost all applications _know_ their
> system configuration. then I don't think api misuse issue is big matter.
No, I don't want to do that. I was just commeting on why existing
solutions are the way they are.
next prev parent reply other threads:[~2012-05-08 8:04 UTC|newest]
Thread overview: 94+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-01 13:24 [PATCH 0/3] vmevent: Implement 'low memory' attribute Anton Vorontsov
2012-05-01 13:25 ` [PATCH 1/3] vmevent: Implement equal-to attribute state Anton Vorontsov
2012-05-01 13:25 ` [PATCH 2/3] vmevent: Pass attr argument to sampling functions Anton Vorontsov
2012-05-01 13:26 ` [PATCH 3/3] vmevent: Implement special low-memory attribute Anton Vorontsov
2012-05-03 10:33 ` Pekka Enberg
2012-05-04 4:26 ` Minchan Kim
2012-05-04 7:38 ` Anton Vorontsov
2012-05-07 7:14 ` Pekka Enberg
2012-05-07 8:26 ` KOSAKI Motohiro
2012-05-07 12:15 ` Anton Vorontsov
2012-05-07 19:19 ` KOSAKI Motohiro
2012-05-08 0:31 ` Anton Vorontsov
2012-05-08 5:20 ` Pekka Enberg
2012-05-08 5:42 ` KOSAKI Motohiro
2012-05-08 5:53 ` Pekka Enberg
2012-05-08 7:11 ` KOSAKI Motohiro
2012-05-08 7:36 ` Pekka Enberg
2012-05-08 7:50 ` KOSAKI Motohiro
2012-05-08 8:03 ` Pekka Enberg [this message]
2012-05-08 9:15 ` leonid.moiseichuk
2012-05-08 9:19 ` Pekka Enberg
2012-05-08 10:38 ` leonid.moiseichuk
2012-06-01 12:21 ` [PATCH 0/5] Some vmevent fixes Anton Vorontsov
2012-06-01 12:24 ` [PATCH 1/5] vmstat: Implement refresh_vm_stats() Anton Vorontsov
2012-06-05 14:30 ` Christoph Lameter
2012-06-08 3:17 ` KOSAKI Motohiro
2012-06-01 12:24 ` [PATCH 2/5] vmevent: Convert from deferred timer to deferred work Anton Vorontsov
2012-06-08 3:25 ` KOSAKI Motohiro
2012-06-08 6:58 ` Anton Vorontsov
2012-06-08 7:03 ` Pekka Enberg
2012-06-08 8:07 ` Anton Vorontsov
2012-06-08 7:05 ` leonid.moiseichuk
2012-06-08 7:10 ` KOSAKI Motohiro
2012-06-08 7:18 ` leonid.moiseichuk
2012-06-08 7:23 ` KOSAKI Motohiro
2012-06-08 7:28 ` leonid.moiseichuk
2012-06-08 7:33 ` KOSAKI Motohiro
2012-06-08 7:49 ` leonid.moiseichuk
2012-06-08 7:58 ` Anton Vorontsov
2012-06-08 8:16 ` leonid.moiseichuk
2012-06-08 8:41 ` Anton Vorontsov
2012-06-08 8:57 ` leonid.moiseichuk
2012-06-08 10:35 ` Anton Vorontsov
2012-06-08 11:03 ` leonid.moiseichuk
2012-06-08 12:13 ` Anton Vorontsov
2012-06-08 12:25 ` leonid.moiseichuk
2012-06-01 12:24 ` [PATCH 3/5] vmevent: Refresh vmstats before sampling Anton Vorontsov
2012-06-05 14:36 ` Christoph Lameter
2012-06-01 12:24 ` [PATCH 4/5] vmevent: Hide meaningful names from the user-visible header Anton Vorontsov
2012-06-01 12:24 ` [PATCH 5/5] vmevent: Rename one-shot mode to edge trigger mode Anton Vorontsov
2012-06-03 18:26 ` [PATCH 0/5] Some vmevent fixes Pekka Enberg
2012-06-04 8:45 ` Minchan Kim
2012-06-04 9:20 ` Pekka Enberg
2012-06-04 12:23 ` Minchan Kim
2012-06-04 11:38 ` Anton Vorontsov
2012-06-04 12:17 ` Minchan Kim
2012-06-04 13:35 ` Anton Vorontsov
2012-06-05 7:53 ` Pekka Enberg
2012-06-05 8:00 ` Minchan Kim
2012-06-05 8:01 ` Pekka Enberg
2012-06-05 8:16 ` leonid.moiseichuk
2012-06-05 8:27 ` Minchan Kim
2012-06-08 3:35 ` KOSAKI Motohiro
2012-06-04 20:05 ` KOSAKI Motohiro
2012-06-04 22:39 ` Anton Vorontsov
2012-06-08 3:45 ` KOSAKI Motohiro
2012-06-08 6:57 ` Pekka Enberg
2012-06-05 7:47 ` Pekka Enberg
2012-06-05 8:39 ` Anton Vorontsov
2012-06-07 2:41 ` Minchan Kim
2012-06-08 7:49 ` Anton Vorontsov
2012-06-08 8:43 ` Minchan Kim
2012-06-08 8:48 ` Pekka Enberg
2012-06-08 9:12 ` leonid.moiseichuk
2012-06-08 9:45 ` Anton Vorontsov
2012-06-08 10:42 ` Minchan Kim
2012-06-08 11:14 ` Anton Vorontsov
2012-06-11 4:50 ` Minchan Kim
2012-06-05 7:52 ` Pekka Enberg
2012-06-08 3:55 ` KOSAKI Motohiro
2012-06-08 6:54 ` Pekka Enberg
2012-06-08 6:57 ` KOSAKI Motohiro
2012-06-08 6:59 ` Pekka Enberg
2012-06-04 19:50 ` KOSAKI Motohiro
2012-05-08 8:32 ` [PATCH 3/3] vmevent: Implement special low-memory attribute Minchan Kim
2012-05-08 9:27 ` Pekka Enberg
2012-06-05 14:40 ` Christoph Lameter
2012-05-08 6:58 ` Anton Vorontsov
2012-05-08 7:16 ` KOSAKI Motohiro
2012-05-08 8:13 ` Anton Vorontsov
2012-05-08 8:21 ` Anton Vorontsov
2012-05-03 8:10 ` [PATCH 0/3] vmevent: Implement 'low memory' attribute Pekka Enberg
2012-05-03 9:44 ` Anton Vorontsov
2012-05-03 10:54 ` Pekka Enberg
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