On Thu, Mar 3, 2022 at 4:15 AM Tianchen Ding <dtcccc@xxxxxxxxxxxxxxxxx> wrote:
KFENCE aims at production environments, but it does not allow enabling
after system startup because kfence_pool only alloc pages from memblock.
Consider the following production scene:
At first, for performance considerations, production machines do not
enable KFENCE.
What are the performance considerations you have in mind? Are you running KFENCE with a very aggressive sampling rate?
However, after running for a while, the kernel is suspected to have
memory errors. (e.g., a sibling machine crashed.)
I have doubts regarding this setup. It might be faster (although one can tune KFENCE to have nearly zero performance impact), but is harder to maintain.
It will also catch fewer errors than if you just had KFENCE on from the very beginning:
- sibling machines may behave differently, and a certain bug may only occur once - in that case the secondary instances won't notice it, even with KFENCE;
- KFENCE also catches non-lethal corruptions (e.g. OOB reads), which may stay under radar for a very long time.
So other production machines need to enable KFENCE, but it's hard for
them to reboot.
The 1st patch allows re-enabling KFENCE if the pool is already
allocated from memblock.
The 2nd patch applies the main part.
Tianchen Ding (2):
kfence: Allow re-enabling KFENCE after system startup
kfence: Alloc kfence_pool after system startup
mm/kfence/core.c | 106 ++++++++++++++++++++++++++++++++++++++---------
1 file changed, 87 insertions(+), 19 deletions(-)
--
2.27.0
Alexander Potapenko
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen, dass die E-Mail an die falsche Person gesendet wurde.
This e-mail is confidential. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it has gone to the wrong person.
Software Engineer
Google Germany GmbH
Erika-Mann-Straße, 33
80636 München
Geschäftsführer: Paul Manicle, Liana Sebastian
Registergericht und -nummer: Hamburg, HRB 86891
Sitz der Gesellschaft: Hamburg
Diese E-Mail ist vertraulich. Falls Sie diese fälschlicherweise erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter, löschen Sie alle Kopien und Anhänge davon und lassen Sie mich bitte wissen, dass die E-Mail an die falsche Person gesendet wurde.
This e-mail is confidential. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it has gone to the wrong person.
