linux-kernel - Re: [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited process killing

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Date:   Thu, 11 Apr 2019 08:33:13 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     akpm@...ux-foundation.org, mhocko@...e.com, rientjes@...gle.com,
        yuzhoujian@...ichuxing.com, jrdr.linux@...il.com, guro@...com,
        hannes@...xchg.org, penguin-kernel@...ove.SAKURA.ne.jp,
        ebiederm@...ssion.com, shakeelb@...gle.com, christian@...uner.io,
        minchan@...nel.org, timmurray@...gle.com, dancol@...gle.com,
        joel@...lfernandes.org, jannh@...gle.com, linux-mm@...ck.org,
        lsf-pc@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        kernel-team@...roid.com
Subject: Re: [RFC 2/2] signal: extend pidfd_send_signal() to allow expedited
 process killing

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?