Re: [PATCH] nptl: Disable THP on thread stack if it incurs in large RSS usage

["Cristian Rodríguez" <cristian@rodriguez.im>]

[-- Attachment #1: Type: text/plain, Size: 1431 bytes --]

On Wed, Jan 31, 2024 at 12:18 PM Cristian Rodríguez <cristian@rodriguez.im>
wrote:

>
>
> On Wed, Jan 31, 2024 at 8:30 AM Adhemerval Zanella Netto <
> adhemerval.zanella@linaro.org> wrote:
>
>>
>>
>> On 31/01/24 04:54, Florian Weimer wrote:
>> > * Cristian Rodríguez:
>> >
>> >> On Tue, May 23, 2023 at 5:48 AM Wilco Dijkstra via Libc-alpha <
>> libc-alpha@sourceware.org>
>> >> wrote:
>> >>
>> >>> However even switching off THP for all small stacks (eg. default size
>> or smaller)
>> >>> would avoid the random use of THP without needing to set the tunable.
>> >>>
>> >>> Cheers,
>> >>> Wilco
>> >>
>> >>
>> >> Didn't found the exact message to reply.. but this one is close
>> enough. MAP_STACK implies no
>> >> transparent hugepages since linux kernel commit
>> >>
>> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c4608d1bf7c6536d1a3d233eb21e50678681564e
>> >
>> > It's an odd choice for fixing the regression.  I commented on the
>> > linux-mm thread.  It's also surprising to see such changes being made
>> > without larger discussion.
>>
>> Do you have a link for this discussion?
>>
>
> Doesn't this also imply that  the kernel expects the MAP_GROWSDOWN flag
> #if _STACK_GROWS_DOWN to do the right thing elsewhere ?
>
>
> Older versions will  need MAP_GROWS* to have identical THP behaviour than
earilier kernel versions it seems to me.

[-- Attachment #2: Type: text/html, Size: 2491 bytes --]