From: Vlastimil Babka <vbabka@suse.cz>
To: Oleksandr Natalenko <oleksandr@redhat.com>,
Michal Hocko <mhocko@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
LKML <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
linux-api@vger.kernel.org, Suren Baghdasaryan <surenb@google.com>,
Tim Murray <timmurray@google.com>,
Daniel Colascione <dancol@google.com>,
Sandeep Patil <sspatil@google.com>,
Sonny Rao <sonnyrao@google.com>,
Brian Geffon <bgeffon@google.com>,
Johannes Weiner <hannes@cmpxchg.org>,
Shakeel Butt <shakeelb@google.com>,
John Dias <joaodias@google.com>,
Joel Fernandes <joel@joelfernandes.org>,
Jann Horn <jannh@google.com>,
alexander.h.duyck@linux.intel.com, sj38.park@gmail.com,
SeongJae Park <sjpark@amazon.de>
Subject: Re: [PATCH v7 7/7] mm/madvise: allow KSM hints for remote API
Date: Mon, 9 Mar 2020 16:42:43 +0100 [thread overview]
Message-ID: <34f812b8-df54-eaad-5cf0-335f07da55c6@suse.cz> (raw)
In-Reply-To: <20200309151932.6sjwq6bucbu6zsea@butterfly.localdomain>
On 3/9/20 4:19 PM, Oleksandr Natalenko wrote:
> On Mon, Mar 09, 2020 at 04:08:15PM +0100, Michal Hocko wrote:
>> On Mon 09-03-20 14:11:17, Oleksandr Natalenko wrote:
>> > On Fri, Mar 06, 2020 at 05:08:18PM +0100, Vlastimil Babka wrote:
>> [...]
>> > > Dunno, it's nice to react to signals quickly, for any proces that gets them, no?
>> >
>> > So, do you mean something like this?
>> >
>> > ===
>> > diff --git a/mm/ksm.c b/mm/ksm.c
>> > index 363ec8189561..b39c237cfcf4 100644
>> > --- a/mm/ksm.c
>> > +++ b/mm/ksm.c
>> > @@ -849,7 +849,8 @@ static int unmerge_ksm_pages(struct vm_area_struct *vma,
>> > for (addr = start; addr < end && !err; addr += PAGE_SIZE) {
>> > if (ksm_test_exit(vma->vm_mm))
>> > break;
>> > - if (signal_pending(current))
>> > + if (signal_pending(current) ||
>> > + signal_pending(rcu_dereference(vma->vm_mm->owner)))
>> > err = -ERESTARTSYS;
>> > else
>> > err = break_ksm(vma, addr);
>> > ===
>>
>> This is broken because mm might be attached to different tasks.
>> AFAIU this check is meant to allow quick backoff of the _calling_
>> process so that it doesn't waste time when the context is killed
>> already. I do not understand why should we care about any other context
>> here? What is the actual problem this would solve?
>
> I agree with you, but still trying to understand what does Vlastimil mean
> :).
Well you wondered if we should stop caring about current, and I said that
probably wouldn't be nice.
As for caring about the other task, patch 3/7 does that for
(MADV_COLD|MADV_PAGEOUT) so I just pointed out that the KSM case doesn't. AFAIU
if we don't check the signals, we might be blocking the killed task from exiting?
>>
>> --
>> Michal Hocko
>> SUSE Labs
>>
>
next prev parent reply other threads:[~2020-03-09 15:42 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-02 19:36 [PATCH v7 0/7] introduce memory hinting API for external process Minchan Kim
2020-03-02 19:36 ` [PATCH v7 1/7] mm: pass task and mm to do_madvise Minchan Kim
2020-03-05 15:48 ` Vlastimil Babka
2020-05-08 18:21 ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 2/7] mm: introduce external memory hinting API Minchan Kim
2020-03-03 10:33 ` kbuild test robot
2020-03-03 14:57 ` Minchan Kim
2020-03-05 18:15 ` Vlastimil Babka
2020-03-10 22:20 ` Minchan Kim
2020-03-11 0:36 ` Minchan Kim
2020-03-12 12:40 ` Vlastimil Babka
2020-03-12 20:23 ` Minchan Kim
2020-05-08 18:33 ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 3/7] mm: check fatal signal pending of target process Minchan Kim
2020-03-06 10:22 ` Vlastimil Babka
2020-03-10 22:24 ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 4/7] pid: move pidfd_get_pid function to pid.c Minchan Kim
2020-03-06 10:57 ` Vlastimil Babka
2020-03-06 11:14 ` Christian Brauner
2020-03-02 19:36 ` [PATCH v7 5/7] mm: support both pid and pidfd for process_madvise Minchan Kim
2020-03-06 11:14 ` Vlastimil Babka
2020-03-11 0:42 ` Minchan Kim
2020-05-08 18:36 ` Minchan Kim
2020-05-08 23:04 ` Andrew Morton
2020-05-09 12:48 ` Christian Brauner
2020-05-09 23:14 ` Minchan Kim
2020-05-12 19:55 ` Suren Baghdasaryan
2020-03-02 19:36 ` [PATCH v7 6/7] mm/madvise: employ mmget_still_valid for write lock Minchan Kim
2020-03-06 12:52 ` Vlastimil Babka
2020-03-06 13:03 ` Oleksandr Natalenko
2020-03-06 16:03 ` Vlastimil Babka
2020-03-09 12:30 ` Oleksandr Natalenko
2020-03-10 22:28 ` Minchan Kim
2020-03-02 19:36 ` [PATCH v7 7/7] mm/madvise: allow KSM hints for remote API Minchan Kim
2020-03-06 13:13 ` Vlastimil Babka
2020-03-06 13:41 ` Oleksandr Natalenko
2020-03-06 16:08 ` Vlastimil Babka
2020-03-09 13:11 ` Oleksandr Natalenko
2020-03-09 15:08 ` Michal Hocko
2020-03-09 15:19 ` Oleksandr Natalenko
2020-03-09 15:42 ` Vlastimil Babka [this message]
2020-03-09 16:03 ` Michal Hocko
2020-06-11 2:21 ` Jann Horn
2020-03-02 21:16 ` [PATCH v7 0/7] introduce memory hinting API for external process Andrew Morton
2020-03-02 21:42 ` Minchan Kim
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