From: Rik van Riel <riel@redhat.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Alex Thorlton <athorlton@sgi.com>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Mel Gorman <mgorman@suse.de>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Johannes Weiner <hannes@cmpxchg.org>,
"Eric W. Biederman" <ebiederm@xmission.com>,
Sedat Dilek <sedat.dilek@gmail.com>,
Frederic Weisbecker <fweisbec@gmail.com>,
Dave Jones <davej@redhat.com>,
Michael Kerrisk <mtk.manpages@gmail.com>,
"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>,
David Howells <dhowells@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
Al Viro <viro@zeniv.linux.org.uk>,
Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
Kees Cook <keescook@chromium.org>, Robin Holt <holt@sgi.com>
Subject: Re: [PATCHv2] Add per-process flag to control thp
Date: Mon, 05 Aug 2013 11:09:20 -0400 [thread overview]
Message-ID: <51FFC020.9040300@redhat.com> (raw)
In-Reply-To: <20130803170102.GD32568@redhat.com>
On 08/03/2013 01:01 PM, Oleg Nesterov wrote:
>> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE
>> + p->thp_disabled = current->thp_disabled;
>> +#endif
>
> Unneeded. It will be copied by dup_task_struct() automagically.
>
> But I simply can't understand why this flag is per-thread. It should be
> mm flag, no?
It has to be per-mm for another reason, too.
Think about what were to happen if one process were ptracing
a process with the thp_disabled flag, and ended up causing a
new anonymous page to be faulted in.
With the thp_disabled flag in the task, get_user_pages would
end up not seeing the flag, and the task could get a transparent
huge page.
With the thp_disabled flag in the mm, it would be possible for
get_user_pages to easily find the flag, and do the right thing.
--
All rights reversed
next prev parent reply other threads:[~2013-08-05 15:10 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-08-02 20:57 [PATCHv2] Add per-process flag to control thp Alex Thorlton
2013-08-03 17:01 ` Oleg Nesterov
2013-08-05 14:45 ` Peter Zijlstra
2013-08-05 15:12 ` Alex Thorlton
2013-08-05 15:05 ` Alex Thorlton
2013-08-05 15:09 ` Rik van Riel [this message]
2013-08-05 23:03 ` Andrew Morton
2013-08-06 15:08 ` Alex Thorlton
2013-08-06 16:04 ` Rik van Riel
2013-08-08 3:49 ` David Rientjes
2013-08-11 16:56 ` Aneesh Kumar K.V
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