From: Pekka Enberg <penberg@kernel.org>
To: leonid.moiseichuk@nokia.com
Cc: riel@redhat.com, minchan@kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, kamezawa.hiroyu@jp.fujitsu.com,
mel@csn.ul.ie, rientjes@google.com, kosaki.motohiro@gmail.com,
hannes@cmpxchg.org, mtosatti@redhat.com,
akpm@linux-foundation.org, rhod@redhat.com,
kosaki.motohiro@jp.fujitsu.com
Subject: Re: [RFC 1/3] /dev/low_mem_notify
Date: Wed, 18 Jan 2012 11:15:41 +0200 [thread overview]
Message-ID: <CAOJsxLGiG_Bsp8eMtqCjFToxYAPCE4HC9XCebpZ+-G8E3gg5bw@mail.gmail.com> (raw)
In-Reply-To: <84FF21A720B0874AA94B46D76DB98269045596AE@008-AM1MPN1-003.mgdnok.nokia.com>
On Wed, Jan 18, 2012 at 11:06 AM, <leonid.moiseichuk@nokia.com> wrote:
> Would be possible to not use percents for thesholds? Accounting in pages even
> not so difficult to user-space.
How does that work with memory hotplug?
On Wed, Jan 18, 2012 at 11:06 AM, <leonid.moiseichuk@nokia.com> wrote:
> Also, looking on vmnotify_match I understand that events propagated to
> user-space only in case threshold trigger change state from 0 to 1 but not
> back, 1-> 0 is very useful event as well.
>
> Would be possible to use for threshold pointed value(s) e.g. according to
> enum zone_state_item, because kinds of memory to track could be different?
> E.g. to tracking paging activity NR_ACTIVE_ANON and NR_ACTIVE_FILE could be
> interesting, not only free.
I don't think there's anything in the ABI that would prevent that.
>> +struct vmnotify_event {
>> + /* Size of the struct for ABI extensibility. */
>> + __u32 size;
>> +
>> + __u64 nr_avail_pages;
>> +
>> + __u64 nr_swap_pages;
>> +
>> + __u64 nr_free_pages;
>> +};
>
> Two fields here most likely session-constant, (nr_avail_pages and
> nr_swap_pages), seems not much sense to report them in every event. If we
> have memory/swap hotplug user-space can use sysinfo() call.
I actually changed the ABI to look like this:
struct vmnotify_event {
/*
* Size of the struct for ABI extensibility.
*/
__u32 size;
__u64 attrs;
__u64 attr_values[];
};
So userspace can decide which fields to include in notifications.
On Wed, Jan 18, 2012 at 11:06 AM, <leonid.moiseichuk@nokia.com> wrote:
>> +static void vmnotify_sample(struct vmnotify_watch *watch) {
> ...
>> + si_meminfo(&si);
>> + event.nr_avail_pages = si.totalram;
>> +
>> +#ifdef CONFIG_SWAP
>> + si_swapinfo(&si);
>> + event.nr_swap_pages = si.totalswap;
>> +#endif
>> +
>
> Why not to use global_page_state() directly? si_meminfo() and especial
> si_swapinfo are quite expensive call.
Sure, we can do that. Feel free to send a patch :-).
>> +static void vmnotify_start_timer(struct vmnotify_watch *watch) {
>> + u64 sample_period = watch->config.sample_period_ns;
>> +
>> + hrtimer_init(&watch->timer, CLOCK_MONOTONIC,
>> HRTIMER_MODE_REL);
>> + watch->timer.function = vmnotify_timer_fn;
>> +
>> + hrtimer_start(&watch->timer, ns_to_ktime(sample_period),
>> +HRTIMER_MODE_REL_PINNED); }
>
> Do I understand correct you allocate timer for every user-space client and
> propagate events every pointed interval? What will happened with system if
> we have a timer but need to turn CPU off? The timer must not be a reason to
> wakeup if user-space is sleeping.
No idea what happens. The sampling code is just a proof of concept thing and I
expect it to be buggy as hell. :-)
Pekka
next prev parent reply other threads:[~2012-01-18 9:15 UTC|newest]
Thread overview: 62+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-17 8:13 [RFC 0/3] low memory notify Minchan Kim
2012-01-17 8:13 ` [RFC 1/3] /dev/low_mem_notify Minchan Kim
2012-01-17 9:27 ` Pekka Enberg
2012-01-17 16:35 ` Rik van Riel
2012-01-17 18:51 ` Pekka Enberg
2012-01-17 19:30 ` Rik van Riel
2012-01-17 19:49 ` Pekka Enberg
2012-01-17 19:54 ` Pekka Enberg
2012-01-17 19:57 ` Pekka Enberg
2012-01-17 23:20 ` Minchan Kim
2012-01-18 7:16 ` Pekka Enberg
2012-01-18 7:49 ` Minchan Kim
2012-01-18 9:06 ` leonid.moiseichuk
2012-01-18 9:15 ` Pekka Enberg [this message]
2012-01-18 9:41 ` leonid.moiseichuk
2012-01-18 10:40 ` Pekka Enberg
2012-01-18 10:44 ` leonid.moiseichuk
2012-01-18 23:34 ` Ronen Hod
2012-01-19 7:25 ` Pekka Enberg
2012-01-19 9:05 ` Ronen Hod
2012-01-19 9:10 ` Pekka Enberg
2012-01-19 9:20 ` Ronen Hod
2012-01-19 10:53 ` leonid.moiseichuk
2012-01-19 11:07 ` Pekka Enberg
2012-01-19 11:54 ` leonid.moiseichuk
2012-01-19 11:59 ` Pekka Enberg
2012-01-19 12:06 ` Pekka Enberg
2012-01-24 15:38 ` Marcelo Tosatti
2012-01-24 16:08 ` Ronen Hod
2012-01-24 18:10 ` Marcelo Tosatti
2012-01-25 8:52 ` Ronen Hod
2012-01-25 10:12 ` Marcelo Tosatti
2012-01-25 10:48 ` Ronen Hod
2012-01-26 16:17 ` Marcelo Tosatti
2012-01-24 16:10 ` Pekka Enberg
2012-01-24 18:29 ` Marcelo Tosatti
2012-01-25 8:19 ` leonid.moiseichuk
2012-01-19 7:34 ` Pekka Enberg
2012-01-24 16:22 ` Arnd Bergmann
2012-01-18 14:30 ` Rik van Riel
2012-01-18 15:29 ` Pekka Enberg
2012-01-24 15:40 ` Marcelo Tosatti
2012-01-24 16:01 ` Pekka Enberg
2012-01-24 16:25 ` Arnd Bergmann
2012-01-24 18:32 ` Marcelo Tosatti
2012-01-24 21:57 ` Jonathan Corbet
2012-01-17 9:45 ` Pekka Enberg
2012-01-17 8:13 ` [RFC 2/3] vmscan hook Minchan Kim
2012-01-17 8:39 ` KAMEZAWA Hiroyuki
2012-01-17 9:13 ` Minchan Kim
2012-01-17 10:05 ` KAMEZAWA Hiroyuki
2012-01-17 23:08 ` Minchan Kim
2012-01-18 0:18 ` KAMEZAWA Hiroyuki
2012-01-18 14:17 ` Rik van Riel
2012-01-19 2:25 ` KAMEZAWA Hiroyuki
2012-01-19 14:42 ` Rik van Riel
2012-01-20 0:24 ` KAMEZAWA Hiroyuki
2012-01-17 8:13 ` [RFC 3/3] test program Minchan Kim
2012-01-17 14:38 ` [RFC 0/3] low memory notify Colin Walters
2012-01-17 15:04 ` Pekka Enberg
2012-01-17 16:44 ` Rik van Riel
2012-01-17 17:16 ` Olof Johansson
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=CAOJsxLGiG_Bsp8eMtqCjFToxYAPCE4HC9XCebpZ+-G8E3gg5bw@mail.gmail.com \
--to=penberg@kernel.org \
--cc=akpm@linux-foundation.org \
--cc=hannes@cmpxchg.org \
--cc=kamezawa.hiroyu@jp.fujitsu.com \
--cc=kosaki.motohiro@gmail.com \
--cc=kosaki.motohiro@jp.fujitsu.com \
--cc=leonid.moiseichuk@nokia.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=mel@csn.ul.ie \
--cc=minchan@kernel.org \
--cc=mtosatti@redhat.com \
--cc=rhod@redhat.com \
--cc=riel@redhat.com \
--cc=rientjes@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).