linux-kernel - Re: [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of number of stacks

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Message-ID: <CALCETrVJP4XO-QLtdMK4Dx_zTFZKKHwe+jGXvoo+ZP=NVSLdBA@mail.gmail.com>
Date:	Thu, 16 Jun 2016 12:20:14 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Vladimir Davydov <vdavydov@...tuozzo.com>
Cc:	Andy Lutomirski <luto@...nel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>, Borislav Petkov <bp@...en8.de>,
	Nadav Amit <nadav.amit@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Brian Gerst <brgerst@...il.com>,
	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Josh Poimboeuf <jpoimboe@...hat.com>,
	Johannes Weiner <hannes@...xchg.org>,
	Michal Hocko <mhocko@...nel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH 04/13] mm: Track NR_KERNEL_STACK in pages instead of
 number of stacks

On Thu, Jun 16, 2016 at 10:21 AM, Andy Lutomirski <luto@...capital.net> wrote:
> On Thu, Jun 16, 2016 at 4:10 AM, Vladimir Davydov
> <vdavydov@...tuozzo.com> wrote:
>> On Wed, Jun 15, 2016 at 05:28:26PM -0700, Andy Lutomirski wrote:
>> ...
>>> @@ -225,7 +225,8 @@ static void account_kernel_stack(struct thread_info *ti, int account)
>>>  {
>>>       struct zone *zone = page_zone(virt_to_page(ti));
>>>
>>> -     mod_zone_page_state(zone, NR_KERNEL_STACK, account);
>>> +     mod_zone_page_state(zone, NR_KERNEL_STACK,
>>> +                         THREAD_SIZE / PAGE_SIZE * account);
>>
>> It won't work if THREAD_SIZE < PAGE_SIZE. Is there an arch with such a
>> thread size, anyway? If no, we should probably drop thread_info_cache.
>
> On a quick grep, I can't find any.  I'll add a BUILD_BUG_ON for now.

Correction.  frv has 16KiB pages and 8KiB stacks.  I'll rework it to
count NR_KERNEL_STACK in KiB.  Sigh.

--Andy

>
> --Andy



-- 
Andy Lutomirski
AMA Capital Management, LLC