Re: [Xen-devel] [PATCH] xen/credit2: Drop unnecessary bit test

2018-01-12 Thread Dario Faggioli
On Thu, 2018-01-11 at 17:36 +, Andrew Cooper wrote: > It is generally worth doing a read to conditionally avoid a locked > RMW, > in the case that you expect the locked RMW to be unnecessary (i.e. > the > modification is already present). > > The same is not true for plain memory reads and

Re: [Xen-devel] [PATCH] xen/credit2: Drop unnecessary bit test

2018-01-11 Thread Dario Faggioli
On Thu, 2018-01-11 at 16:50 +, George Dunlap wrote: > On 01/11/2018 04:48 PM, Andrew Cooper wrote: > > Signed-off-by: Andrew Cooper > > --- > > CC: George Dunlap > > CC: Dario Faggioli > > > > Notices by chance

Re: [Xen-devel] [PATCH] xen/credit2: Drop unnecessary bit test

2018-01-11 Thread George Dunlap
On 01/11/2018 04:48 PM, Andrew Cooper wrote: > Signed-off-by: Andrew Cooper > --- > CC: George Dunlap > CC: Dario Faggioli > > Notices by chance while inspecting the disassembly delta for "x86/bitops: > Introduce