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SubjectRe: [RFC] mlock: release mmap_sem every 256 faulted pages
Date

minor additionl comments.

> + /*
> + * Limit batch size to 256 pages in order to reduce
> + * mmap_sem hold time.
> + */
> + nfault = nstart + 256 * PAGE_SIZE;

You made 256 pages batch and __mlock_vma_pages_range() has 16 pages
another batch.
Can we unify this two batch?

Plus, PeterZ implemeted mutex contention detect method (see "[PATCH 18/21]
mutex: Provide mutex_is_contended"). now you can easily implemnt akpm proposed
efficient batching.

Thanks.


> +
> + /*
> + * Now fault in a batch of pages. We need to check the vma
> + * flags again, as we've not been holding mmap_sem.
> + */
> + if ((vma->vm_flags & (VM_DONTEXPAND | VM_RESERVED)) ||
> + is_vm_hugetlb_page(vma) || vma == get_gate_vma(current)) {
> + if (nfault < nend)
> + nend = nfault;
> + make_pages_present(nstart, nend);
> + } else if (vma->vm_flags & VM_LOCKED) {
> + if (nfault < nend)
> + nend = nfault;
> + error = __mlock_vma_pages_range(vma, nstart, nend);
> + }
> + up:
> + up_read(&mm->mmap_sem);
> + if (error)
> + return __mlock_posix_error_return(error);
> + }
> + return 0;
> +}




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