[dpdk-dev] vhost-user technical isssues

[Tetsuya Mukawa]

Hi Xie,

(2014/11/14 19:59), Xie, Huawei wrote:
> I tested with latest qemu(with offset fix) in vhost app(not with test case), unmap succeeds only when the size is aligned to 1GB(hugepage size).
I appreciate for your testing.

> Another important thing is  could we do mmap(0, region[i].memory_size, PROT_XX, mmap_offset) rather than with offset 0? With the region above 4GB, we will waste 4GB address space. Or we at least need to round down offset to nearest 1GB, and round up memory size to upper 1GB, to save some address space waste.
>
> Anyway, this is ugly. Kernel doesn't take care of us, do those alignment for us automatically.
>

It seems 'offset' also should be aligned by hugepage size also.
But it might be a specification of mmap. Manpage of mmap says 'offset'
should be aligned by sysconf(_SC_PAGE_SIZE).
If the target file is on hugetlbfs, I guess hugepage size is used as
alignment size.

Thanks,
Tetsuya