RE: [PATCH 1/1] Drivers: base: memory: Export symbols for onliningmemory blocks

From: KY Srinivasan
Date: Thu Jul 25 2013 - 07:16:00 EST

> -----Original Message-----
> From: Michal Hocko [mailto:mhocko@xxxxxxx]
> Sent: Thursday, July 25, 2013 3:57 AM
> To: Dave Hansen
> Cc: KY Srinivasan; Dave Hansen; gregkh@xxxxxxxxxxxxxxxxxxx; linux-
> kernel@xxxxxxxxxxxxxxx; devel@xxxxxxxxxxxxxxxxxxxxxx; olaf@xxxxxxxxx;
> apw@xxxxxxxxxxxxx; andi@xxxxxxxxxxxxxx; akpm@xxxxxxxxxxxxxxxxxxxx; linux-
> mm@xxxxxxxxx; kamezawa.hiroyuki@xxxxxxxxx; hannes@xxxxxxxxxxx;
> yinghan@xxxxxxxxxx; jasowang@xxxxxxxxxx; kay@xxxxxxxx
> Subject: Re: [PATCH 1/1] Drivers: base: memory: Export symbols for onlining
> memory blocks
> On Wed 24-07-13 14:02:32, Dave Hansen wrote:
> > On 07/24/2013 12:45 PM, KY Srinivasan wrote:
> > > All I am saying is that I see two classes of failures: (a) Our
> > > inability to allocate memory to manage the memory that is being hot added
> > > and (b) Our inability to bring the hot added memory online within a
> reasonable
> > > amount of time. I am not sure the cause for (b) and I was just speculating that
> > > this could be memory related. What is interesting is that I have seen failure
> related
> > > to our inability to online the memory after having succeeded in hot adding the
> > > memory.
> >
> > I think we should hold off on this patch and other like it until we've
> > been sufficiently able to explain how (b) happens.
> Agreed.

As promised, I have sent out the patches for (a) an implementation of an in-kernel API
for onlining and a consumer for this API. While I don't know the exact reason why the
user mode code is delayed (under some low memory conditions), what is the harm in having
a mechanism to online memory that has been hot added without involving user space code.
Based on Michal's feedback, the onlininig API hides all of the internal details and presents a
generic interface.


K. Y

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