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Date:   Thu, 11 Apr 2019 13:05:40 -0400
From:   Johannes Weiner <hannes@cmpxchg.org>
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Suren Baghdasaryan <surenb@google.com>, akpm@linux-foundation.org,
        mhocko@suse.com, rientjes@google.com, yuzhoujian@didichuxing.com,
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        jannh@google.com, linux-mm@kvack.org,
        lsf-pc@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        kernel-team@android.com
Subject: Re: [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited
 process killing
Message-ID: <20190411170540.GA5136@cmpxchg.org>
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 <20190411014353.113252-3-surenb@google.com>
 <20190411153313.GE22763@bombadil.infradead.org>
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On Thu, Apr 11, 2019 at 08:33:13AM -0700, Matthew Wilcox wrote:
> On Wed, Apr 10, 2019 at 06:43:53PM -0700, Suren Baghdasaryan wrote:
> > Add new SS_EXPEDITE flag to be used when sending SIGKILL via
> > pidfd_send_signal() syscall to allow expedited memory reclaim of the
> > victim process. The usage of this flag is currently limited to SIGKILL
> > signal and only to privileged users.
> 
> What is the downside of doing expedited memory reclaim?  ie why not do it
> every time a process is going to die?

I agree with this. The oom reaper mostly does work the exiting task
would have to do anyway, so this shouldn't be measurably more
expensive to do it per default. I wouldn't want to add a new interface
unless we really do need that type of control.