Re: [Xen-devel] gfn_lock() seems useless.

[Andres Lagar Cavilla <andres@xxxxxxxxxxxxxxxx>]

At the time, I had a patch queue for splitting the p2m locking into a tree of per-2M locks. Very similar to Linux's split locks. I scaffolded the macros to allow for that expansion. Then, I got pulled onto other things.

Andres

On Tue, Feb 2, 2016 at 8:26 AM, Jan Beulich <JBeulich@xxxxxxxx> wrote:

>>> On 02.02.16 at 07:54, <oscar.zhangbo@xxxxxxxxxx> wrote:
> Hi all:
> In patch e1e40bccee7490a01ac7d1f759ec2bbafd3c7185, it says that"many
> routines can logically assert holding the p2m *FOR A SPECIFIC GFN.*" ,
> But I find out that it did nothing for locking a single gfn, in fact it
> still locked the entire p2m list.
>
> -#define p2m_lock_recursive(p) mm_lock_recursive(p2m, &(p)->lock)
> +#define gfn_lock(p,g,o)Â Â Â Âmm_lock_recursive(p2m, &(p)->lock)Â //'g' is not
> used. The entire p2m list is locked.
>
>
> Do we have any plan to lock a specific gfn?

This indeed is a long term plan, but afaik no-one is currently
doing any work in that direction.

Jan

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