Re: [PATCH V4 2/6] mm: mlock: Add new mlock, munlock, and munlockall system calls

Michael Ellerman
2015-07-22T01:25:22Z

On Tue, 2015-07-21 at 13:44 -0700, Andrew Morton wrote:
> On Tue, 21 Jul 2015 15:59:37 -0400 Eric B Munson <emunson@akamai.com> wrote:
>
> > With the refactored mlock code, introduce new system calls for mlock,
> > munlock, and munlockall. The new calls will allow the user to specify
> > what lock states are being added or cleared. mlock2 and munlock2 are
> > trivial at the moment, but a follow on patch will add a new mlock state
> > making them useful.
> >
> > munlock2 addresses a limitation of the current implementation. If a
> > user calls mlockall(MCL_CURRENT | MCL_FUTURE) and then later decides
> > that MCL_FUTURE should be removed, they would have to call munlockall()
> > followed by mlockall(MCL_CURRENT) which could potentially be very
> > expensive. The new munlockall2 system call allows a user to simply
> > clear the MCL_FUTURE flag.
>
> This is hard. Maybe we shouldn't have wired up anything other than
> x86. That's what we usually do with new syscalls.

Yeah I think so.

You haven't wired it up properly on powerpc, but I haven't mentioned it because
I'd rather we did it.

cheers