Re: [dpdk-dev] [PATCH v3] eal: allow hugetlbfs sub-directories

[John Levon <john.levon@nutanix.com>]

On Thu, Jul 22, 2021 at 10:29:45PM +0200, David Marchand wrote:

> On Thu, Jul 8, 2021 at 1:00 PM John Levon <john.levon@nutanix.com> wrote:
> >
> > get_hugepage_dir() was implemented in such a way that a --huge-dir
> > option had to exactly match the mountpoint, but there's no reason for
> > this restriction. Fix the implementation to allow a sub-directory within
> > a suitable hugetlbfs mountpoint to be specified, preferring the closest
> > match.
> >
> > Signed-off-by: John Levon <john.levon@nutanix.com>
> 
> This change in EAL hugetlbfs discovery is too dangerous to be taken after -rc1.

Sure.

> Could you give some usecases/examples on why this change is needed?

Would you like me to expand the commit message? I had hoped it was clear enough,
but I suppose not. Simply put, DPDK above is assuming its the only user of
hugepages on the system - including clear_hugedir(). That is certainly not the
case for our use cases.

> Updating the documentation

https://doc.dpdk.org/guides/linux_gsg/linux_eal_parameters.html

"""
--huge-dir <path to hugetlbfs directory>

Use specified hugetlbfs directory instead of autodetected ones.
"""

That is, it already says "directory", not "mount". You'd like something
additional saying it can be below a mount point?

> and the unit test also seem necessary.

You're talking about app/test/test_eal_flags.c or something else?

thanks,
john