gfn_lock() seems useless.

gfn_lock() seems useless.

[Zhangbo (Oscar)]

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)       mm_lock_recursive(p2m, &(p)->lock)  //'g' is not used. The entire p2m list is locked.


Do we have any plan to lock a specific gfn? If so, how ? If not, shall we redefine the macro? 

Thans.

Oscar.

Re: gfn_lock() seems useless.

[Jan Beulich]

>>> On 02.02.16 at 07:54, <oscar.zhangbo@huawei.com> 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)       mm_lock_recursive(p2m, &(p)->lock)  //'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

Re: gfn_lock() seems useless.

[Andres Lagar Cavilla]

[-- Attachment #1.1: Type: text/plain, Size: 1010 bytes --]

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@suse.com> wrote:

> >>> On 02.02.16 at 07:54, <oscar.zhangbo@huawei.com> 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)       mm_lock_recursive(p2m, &(p)->lock)  //'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
>
>

[-- Attachment #1.2: Type: text/html, Size: 1600 bytes --]

[-- Attachment #2: Type: text/plain, Size: 126 bytes --]

_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xen.org
http://lists.xen.org/xen-devel

Re: gfn_lock() seems useless.

[Konrad Rzeszutek Wilk]

On Tue, Feb 02, 2016 at 08:55:50PM -0800, Andres Lagar Cavilla wrote:
> 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.

Could you post/point folks to your patch queue?

Thanks.
> 
> Andres
> 
> On Tue, Feb 2, 2016 at 8:26 AM, Jan Beulich <JBeulich@suse.com> wrote:
> 
> > >>> On 02.02.16 at 07:54, <oscar.zhangbo@huawei.com> 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)       mm_lock_recursive(p2m, &(p)->lock)  //'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
> >
> >

> _______________________________________________
> Xen-devel mailing list
> Xen-devel@lists.xen.org
> http://lists.xen.org/xen-devel