Re: [PATCHv2] Add per-process flag to control thp

From: Rik van Riel
Date: Mon Aug 05 2013 - 11:10:46 EST

On 08/03/2013 01:01 PM, Oleg Nesterov wrote:

+ p->thp_disabled = current->thp_disabled;

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
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at