Messages in this thread | | | Date | Thu, 13 Oct 2022 18:44:55 +0800 | Subject | Re: [External] Re: [RFC] mm: add new syscall pidfd_set_mempolicy() | From | Zhongkun He <> |
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> On Wed 12-10-22 19:22:21, Zhongkun He wrote: >>> >>> Yes, this will require some refactoring and one potential way is to make >>> mpol ref counting unconditional. The conditional ref. counting has >>> already caused issues in the past and the code is rather hard to follow >>> anyway. I am not really sure this optimization is worth it. >>> >>> Another option would be to block the pidfd side of things on completion >>> which would wake it up from the task_work context but I would rather >>> explore the ref counting approach first and only if this is proven to be >>> too expensive to go with hacks like this. >> >> Hi Michal >> >> The counting approach means executing mpol_get/put() when start/finish using >> mempolicy,right? > > We already do that via mpol_{get,put} but there are cases where the > reference counting is ignored because it cannot be freed and also mpol_cond_put > resp. open coded versions of mpol_needs_cond_ref.
Hi Michal
Could we try to change the MPOL_F_SHARED flag to MPOL_F_STATIC to mark static mempolicy which cannot be freed, and mpol_needs_cond_ref can use MPOL_F_STATIC to avoid freeing the static mempolicy. MPOL_F_SHARED loses its original meaning in counting approach.
Thanks.
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