Subject: Re: LK_SHARED for VFS_VGET/FHTOVP
To: None <firstname.lastname@example.org>
From: YAMAMOTO Takashi <email@example.com>
Date: 05/26/2004 10:05:05
> While not the most concurrent, our VOP interface was pretty MP-safe. Since
> all the locks were exclusive, you could have as many threads wandering
> around in the vnode system, on as many CPUs as you wanted. So once all the
> systems below the VOP layer (the buffer cache and the vm cache and the
> disk drivers) were MP-safe, it would be reasonable to start letting some
> file operations past the big-lock. Since the buffer cache and vm cache
> have been MP-ified, we are actually close to that. The bottom-half of the
> kernel is the only remaining issue.
i don't think that my proposed change affects mp-safeness much.
> However as we start using LK_SHARED, the only thing that is keeping the
> VOP interface safe is our use of big-lock in the kernel. That's a step
> backwards for SMP, in my opinion.
can you please be more specific?
i know atime-update in VOP_READ is protected only by biglock.
(i don't think it's a major problem, though.)
do you know examples other than it?