Messages in this thread | | | Subject | Re: [PATCH v8 2/9] mmap: make mlock_future_check() global | From | David Hildenbrand <> | Date | Thu, 12 Nov 2020 17:22:00 +0100 |
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On 10.11.20 19:06, Mike Rapoport wrote: > On Tue, Nov 10, 2020 at 06:17:26PM +0100, David Hildenbrand wrote: >> On 10.11.20 16:14, Mike Rapoport wrote: >>> From: Mike Rapoport <rppt@linux.ibm.com> >>> >>> It will be used by the upcoming secret memory implementation. >>> >>> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com> >>> --- >>> mm/internal.h | 3 +++ >>> mm/mmap.c | 5 ++--- >>> 2 files changed, 5 insertions(+), 3 deletions(-) >>> >>> diff --git a/mm/internal.h b/mm/internal.h >>> index c43ccdddb0f6..ae146a260b14 100644 >>> --- a/mm/internal.h >>> +++ b/mm/internal.h >>> @@ -348,6 +348,9 @@ static inline void munlock_vma_pages_all(struct vm_area_struct *vma) >>> extern void mlock_vma_page(struct page *page); >>> extern unsigned int munlock_vma_page(struct page *page); >>> +extern int mlock_future_check(struct mm_struct *mm, unsigned long flags, >>> + unsigned long len); >>> + >>> /* >>> * Clear the page's PageMlocked(). This can be useful in a situation where >>> * we want to unconditionally remove a page from the pagecache -- e.g., >>> diff --git a/mm/mmap.c b/mm/mmap.c >>> index 61f72b09d990..c481f088bd50 100644 >>> --- a/mm/mmap.c >>> +++ b/mm/mmap.c >>> @@ -1348,9 +1348,8 @@ static inline unsigned long round_hint_to_min(unsigned long hint) >>> return hint; >>> } >>> -static inline int mlock_future_check(struct mm_struct *mm, >>> - unsigned long flags, >>> - unsigned long len) >>> +int mlock_future_check(struct mm_struct *mm, unsigned long flags, >>> + unsigned long len) >>> { >>> unsigned long locked, lock_limit; >>> >> >> So, an interesting question is if you actually want to charge secretmem >> pages against mlock now, or if you want a dedicated secretmem cgroup >> controller instead? > > Well, with the current implementation there are three limits an > administrator can use to control secretmem limits: mlock, memcg and > kernel parameter. > > The kernel parameter puts a global upper limit for secretmem usage, > memcg accounts all secretmem allocations, including the unused memory in > large pages caching and mlock allows per task limit for secretmem > mappings, well, like mlock does. > > I didn't consider a dedicated cgroup, as it seems we already have enough > existing knobs and a new one would be unnecessary.
To me it feels like the mlock() limit is a wrong fit for secretmem. But maybe there are other cases of using the mlock() limit without actually doing mlock() that I am not aware of (most probably :) )?
I mean, my concern is not earth shattering, this can be reworked later. As I said, it just feels wrong.
-- Thanks,
David / dhildenb
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