From: Michal Hocko <mhocko@kernel.org>
To: Shawn Landden <slandden@gmail.com>
Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-mm@kvack.org, linux-api@vger.kernel.org
Subject: Re: [RFC v2] prctl: prctl(PR_SET_IDLE, PR_IDLE_MODE_KILLME), for stateless idle loops
Date: Fri, 3 Nov 2017 10:09:15 +0100 [thread overview]
Message-ID: <20171103090915.uuaqo56phdbt6gnf@dhcp22.suse.cz> (raw)
In-Reply-To: <20171103063544.13383-1-slandden@gmail.com>
On Thu 02-11-17 23:35:44, Shawn Landden wrote:
> It is common for services to be stateless around their main event loop.
> If a process sets PR_SET_IDLE to PR_IDLE_MODE_KILLME then it
> signals to the kernel that epoll_wait() and friends may not complete,
> and the kernel may send SIGKILL if resources get tight.
>
> See my systemd patch: https://github.com/shawnl/systemd/tree/prctl
>
> Android uses this memory model for all programs, and having it in the
> kernel will enable integration with the page cache (not in this
> series).
>
> 16 bytes per process is kinda spendy, but I want to keep
> lru behavior, which mem_score_adj does not allow. When a supervisor,
> like Android's user input is keeping track this can be done in user-space.
> It could be pulled out of task_struct if an cross-indexing additional
> red-black tree is added to support pid-based lookup.
This is still an abuse and the patch is wrong. We really do have an API
to use I fail to see why you do not use it.
[...]
> @@ -1018,6 +1060,24 @@ bool out_of_memory(struct oom_control *oc)
> return true;
> }
>
> + /*
> + * Check death row for current memcg or global.
> + */
> + l = oom_target_get_queue(current);
> + if (!list_empty(l)) {
> + struct task_struct *ts = list_first_entry(l,
> + struct task_struct, se.oom_target_queue);
> +
> + pr_debug("Killing pid %u from EPOLL_KILLME death row.",
> + ts->pid);
> +
> + /* We use SIGKILL instead of the oom killer
> + * so as to cleanly interrupt ep_poll()
> + */
> + send_sig(SIGKILL, ts, 1);
> + return true;
> + }
Still not NUMA aware and completely backwards. If this is a memcg OOM
then it is _memcg_ to evaluate not the current. The oom might happen up
the hierarchy due to hard limit.
But still, you should be very clear _why_ the existing oom tuning is not
appropropriate and we can think of a way to hanle it better but cramming
the oom selection this way is simply not acceptable.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2017-11-03 9:09 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-01 5:32 [RFC] EPOLL_KILLME: New flag to epoll_wait() that subscribes process to death row (new syscall) Shawn Landden
2017-11-01 14:04 ` Matthew Wilcox
2017-11-01 15:16 ` Colin Walters
2017-11-01 15:22 ` Colin Walters
2017-11-03 9:22 ` peter enderborg
[not found] ` <CA+49okox_Hvg-dGyjZc3u0qLz1S=LJjS4-WT6SxQ9qfPyp6BjQ@mail.gmail.com>
2017-11-01 19:37 ` Colin Walters
2017-11-02 15:24 ` Shawn Paul Landden
2017-11-01 22:10 ` Tetsuo Handa
2017-11-02 15:45 ` Michal Hocko
2017-11-03 6:35 ` [RFC v2] prctl: prctl(PR_SET_IDLE, PR_IDLE_MODE_KILLME), for stateless idle loops Shawn Landden
2017-11-03 9:09 ` Michal Hocko [this message]
2017-11-18 20:33 ` Shawn Landden
[not found] ` <CA+49okqZ8CME0EN1xS_cCTc5Q-fGRreg0makhzNNuRpGs3mjfw@mail.gmail.com>
2017-11-19 4:19 ` Matthew Wilcox
2017-11-20 8:35 ` Michal Hocko
2017-11-21 4:48 ` Shawn Landden
2017-11-21 7:05 ` Michal Hocko
2017-11-15 21:11 ` Pavel Machek
2017-11-21 4:49 ` [RFC v3] It is common for services to be stateless around their main event loop. If a process sets PR_SET_IDLE to PR_IDLE_MODE_KILLME then it signals to the kernel that epoll_wait() and friends may not complete, and the kernel may send SIGKILL if resources get tight Shawn Landden
2017-11-21 4:56 ` Shawn Landden
2017-11-21 5:16 ` [RFC v4] " Shawn Landden
2017-11-21 5:26 ` Shawn Landden
2017-11-21 9:14 ` Thomas Gleixner
2017-11-22 10:29 ` [RFC v2] prctl: prctl(PR_SET_IDLE, PR_IDLE_MODE_KILLME), for stateless idle loops peter enderborg
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