search for: callee_saved

...y on the exact layout of the steal_time structure. Maybe the > > constant 16 can be passed in as a parameter offsetof(struct > > kvm_steal_time, preempted) to the asm call. Yeah it should be well possible to pass that in. But ideally we'd have GCC grow something like __attribute__((callee_saved)) or somesuch and it would do all this for us. > One more thing, that will improve KVM performance, but it won't help Xen. People still use Xen? ;-) In any case, their implementation looks very similar and could easily crib this. > I looked into the assembly code for rwsem_spin_on_owne...

...y on the exact layout of the steal_time structure. Maybe the > > constant 16 can be passed in as a parameter offsetof(struct > > kvm_steal_time, preempted) to the asm call. Yeah it should be well possible to pass that in. But ideally we'd have GCC grow something like __attribute__((callee_saved)) or somesuch and it would do all this for us. > One more thing, that will improve KVM performance, but it won't help Xen. People still use Xen? ;-) In any case, their implementation looks very similar and could easily crib this. > I looked into the assembly code for rwsem_spin_on_owne...

On 02/10/2017 11:19 AM, Peter Zijlstra wrote: > On Fri, Feb 10, 2017 at 10:43:09AM -0500, Waiman Long wrote: >> It was found when running fio sequential write test with a XFS ramdisk >> on a VM running on a 2-socket x86-64 system, the %CPU times as reported >> by perf were as follows: >> >> 69.75% 0.59% fio [k] down_write >> 69.15% 0.01% fio [k]

On 02/10/2017 11:19 AM, Peter Zijlstra wrote: > On Fri, Feb 10, 2017 at 10:43:09AM -0500, Waiman Long wrote: >> It was found when running fio sequential write test with a XFS ramdisk >> on a VM running on a 2-socket x86-64 system, the %CPU times as reported >> by perf were as follows: >> >> 69.75% 0.59% fio [k] down_write >> 69.15% 0.01% fio [k]