linux-kernel - Re: [PATCH 01/11] x86/mm/pat: Don't free PGD entries on memory unmap

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Message-ID: <CALCETrV-Y90=wXOuXGauT0BQbyHdkpfLmi1nF5Y2G=Vhx3GzuA@mail.gmail.com>
Date:	Tue, 22 Sep 2015 11:03:25 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Ingo Molnar <mingo@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-mm <linux-mm@...ck.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Brian Gerst <brgerst@...il.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>, Oleg Nesterov <oleg@...hat.com>,
	Waiman Long <waiman.long@...com>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH 01/11] x86/mm/pat: Don't free PGD entries on memory unmap

On Tue, Sep 22, 2015 at 10:41 AM, Linus Torvalds
<torvalds@...ux-foundation.org> wrote:
> On Mon, Sep 21, 2015 at 11:23 PM, Ingo Molnar <mingo@...nel.org> wrote:
>>
>> This complicates PGD management, so don't do this. We can keep the
>> PGD mapped and the PUD table all clear - it's only a single 4K page
>> per 512 GB of memory mapped.
>
> I'm ok with this just from a "it removes code" standpoint.  That said,
> some of the other patches here make me go "hmm". I'll answer them
> separately.
>

If we want to get rid of vmalloc faults, then this patch makes it much
more obvious that it can be done without hurting performance.

>                   Linus



-- 
Andy Lutomirski
AMA Capital Management, LLC
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