linux-kernel - Re: [PATCH 2/2] mm, memory_hotplug: remove timeout from __offline

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Message-ID: <20170904090114.mrjxipvucieadxa6@dhcp22.suse.cz>
Date:   Mon, 4 Sep 2017 11:01:14 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Xishi Qiu <qiuxishi@...wei.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        Igor Mammedov <imammedo@...hat.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>, linux-mm@...ck.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/2] mm, memory_hotplug: remove timeout from
 __offline_memory

On Mon 04-09-17 16:58:30, Xishi Qiu wrote:
> On 2017/9/4 16:21, Michal Hocko wrote:
> 
> > From: Michal Hocko <mhocko@...e.com>
> > 
> > We have a hardcoded 120s timeout after which the memory offline fails
> > basically since the hot remove has been introduced. This is essentially
> > a policy implemented in the kernel. Moreover there is no way to adjust
> > the timeout and so we are sometimes facing memory offline failures if
> > the system is under a heavy memory pressure or very intensive CPU
> > workload on large machines.
> > 
> > It is not very clear what purpose the timeout actually serves. The
> > offline operation is interruptible by a signal so if userspace wants
> 
> Hi Michal,
> 
> If the user know what he should do if migration for a long time,
> it is OK, but I don't think all the users know this operation
> (e.g. ctrl + c) and the affect.

How is this operation any different from other potentially long
interruptible syscalls?

-- 
Michal Hocko
SUSE Labs