Xen devel - Sep 2013 - [PATCH] Bug-fixes to enable PV ticketlock to work under Xen PVHVM with Linux v3.12. (v1)

After a bit of false starts, lots of debugging, and tons of help from Stefano
and
David on how event mechanism is suppose to work I am happy to present a set
of bug-fixes that make PV ticketlocks work under Xen PVHVM with Linux v3.12.

v3.12 has now thanks to commit 816434ec4a674fcdb3c2221a6dffdc8f34020550
(Merge branch ''x86-spinlocks-for-linus'' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip)
PV ticketlocks. That means:
 - Xen PV bytelock has been replaced by Xen PV ticketlock.
 - Xen PVHVM is using ticketlock (not PV variant) - this patch makes it PV.
 - baremetal is still using ticketlocks.

In other words everything in the kernel is ticketlock based with the
virtualizations
having the ''PV'' part to aid.

Please take a look at the patches. If you are interested in testing them
out I will post a git tree on Monday based on v3.11 and v3.12-rc0. 

Note that I had not run any performance tests and I am not sure when I will
be able to (got other bugs to squash now). I''ve asked our internal
performance
engineer to do some benchmarking - but those results won''t be available
for
some time as it takes time to do good benchmarking.

 arch/x86/xen/enlighten.c |    1 -
 arch/x86/xen/smp.c       |   17 +++++++++++++++++
 arch/x86/xen/spinlock.c  |   45 ++++++++-------------------------------------
 3 files changed, 25 insertions(+), 38 deletions(-)

(oh neat, more deletions!) 

Konrad Rzeszutek Wilk (5):
      xen/spinlock: Fix locking path engaging too soon under PVHVM.
      xen/spinlock: We don''t need the old structure anymore
      xen/smp: Update pv_lock_ops functions before alternative code starts under
PVHVM
      xen/spinlock: Don''t setup xen spinlock IPI kicker if disabled.
      Revert "xen/spinlock: Disable IRQ spinlock (PV) allocation on
PVHVM"

On 07/09/13 14:46, Konrad Rzeszutek Wilk wrote:
> After a bit of false starts, lots of debugging, and tons of help from
Stefano and
> David on how event mechanism is suppose to work I am happy to present a set
> of bug-fixes that make PV ticketlocks work under Xen PVHVM with Linux
v3.12.
> 
> v3.12 has now thanks to commit 816434ec4a674fcdb3c2221a6dffdc8f34020550
> (Merge branch ''x86-spinlocks-for-linus'' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip)
> PV ticketlocks. That means:
>  - Xen PV bytelock has been replaced by Xen PV ticketlock.
>  - Xen PVHVM is using ticketlock (not PV variant) - this patch makes it PV.
>  - baremetal is still using ticketlocks.
> 
> In other words everything in the kernel is ticketlock based with the
virtualizations
> having the ''PV'' part to aid.
> 
> Please take a look at the patches. If you are interested in testing them
> out I will post a git tree on Monday based on v3.11 and v3.12-rc0. 
> 
> Note that I had not run any performance tests and I am not sure when I will
> be able to (got other bugs to squash now). I''ve asked our internal
performance
> engineer to do some benchmarking - but those results won''t be
available for
> some time as it takes time to do good benchmarking.
If there was favourable performance data I would be happy for these to
go in 3.12, without I think they''ll have to wait for 3.13.

David

On Mon, Sep 09, 2013 at 11:34:42AM +0100, David Vrabel
wrote:
> On 07/09/13 14:46, Konrad Rzeszutek Wilk wrote:
> > After a bit of false starts, lots of debugging, and tons of help from
Stefano and
> > David on how event mechanism is suppose to work I am happy to present
a set
> > of bug-fixes that make PV ticketlocks work under Xen PVHVM with Linux
v3.12.
> > 
> > v3.12 has now thanks to commit
816434ec4a674fcdb3c2221a6dffdc8f34020550
> > (Merge branch ''x86-spinlocks-for-linus'' of
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip)
> > PV ticketlocks. That means:
> >  - Xen PV bytelock has been replaced by Xen PV ticketlock.
> >  - Xen PVHVM is using ticketlock (not PV variant) - this patch makes
it PV.
> >  - baremetal is still using ticketlocks.
> > 
> > In other words everything in the kernel is ticketlock based with the
virtualizations
> > having the ''PV'' part to aid.
> > 
> > Please take a look at the patches. If you are interested in testing
them
> > out I will post a git tree on Monday based on v3.11 and v3.12-rc0. 
> > 
> > Note that I had not run any performance tests and I am not sure when I
will
> > be able to (got other bugs to squash now). I''ve asked our
internal performance
> > engineer to do some benchmarking - but those results won''t be
available for
> > some time as it takes time to do good benchmarking.
> 
> If there was favourable performance data I would be happy for these to
> go in 3.12, without I think they''ll have to wait for 3.13.
Then they will have to wait.

I am not going to be able to provide those within this
month.
> 
> David
> 
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