similar to: [PATCH v3 0/2] x86/kvm: Reduce vcpu_is_preempted() overhead

v3->v4: - Fix x86-32 build error. v2->v3: - Provide an optimized __raw_callee_save___kvm_vcpu_is_preempted() in assembly as suggested by PeterZ. - Add a new patch to change vcpu_is_preempted() argument type to long to ease the writing of the assembly code. v1->v2: - Rerun the fio test on a different system on both bare-metal and a KVM guest. Both sockets were

v3->v4: - Fix x86-32 build error. v2->v3: - Provide an optimized __raw_callee_save___kvm_vcpu_is_preempted() in assembly as suggested by PeterZ. - Add a new patch to change vcpu_is_preempted() argument type to long to ease the writing of the assembly code. v1->v2: - Rerun the fio test on a different system on both bare-metal and a KVM guest. Both sockets were

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] call_rwsem_down_write_failed 67.12% 1.12% fio [k] rwsem_down_write_failed 63.48% 52.77% fio [k] osq_lock 9.46% 7.88% fio [k]

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] call_rwsem_down_write_failed 67.12% 1.12% fio [k] rwsem_down_write_failed 63.48% 52.77% fio [k] osq_lock 9.46% 7.88% 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]

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 Mon, Feb 13, 2017 at 05:34:01PM -0500, Waiman Long wrote: > It is the address of &steal_time that will exceed the 32-bit limit. That seems extremely unlikely. That would mean we have more than 4G worth of per-cpu variables declared in the kernel.

On Mon, Feb 13, 2017 at 05:34:01PM -0500, Waiman Long wrote: > It is the address of &steal_time that will exceed the 32-bit limit. That seems extremely unlikely. That would mean we have more than 4G worth of per-cpu variables declared in the kernel.

On Wed, Feb 15, 2017 at 04:37:50PM -0500, Waiman Long wrote: > +/* > + * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and > + * restoring to/from the stack. It is assumed that the preempted value > + * is at an offset of 16 from the beginning of the kvm_steal_time structure > + * which is verified by the BUILD_BUG_ON() macro below. > + */ > +#define

On Wed, Feb 15, 2017 at 04:37:50PM -0500, Waiman Long wrote: > +/* > + * Hand-optimize version for x86-64 to avoid 8 64-bit register saving and > + * restoring to/from the stack. It is assumed that the preempted value > + * is at an offset of 16 from the beginning of the kvm_steal_time structure > + * which is verified by the BUILD_BUG_ON() macro below. > + */ > +#define

It was found when running fio sequential write test with a XFS ramdisk on a KVM guest 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] call_rwsem_down_write_failed 67.12% 1.12% fio [k] rwsem_down_write_failed 63.48% 52.77% fio [k] osq_lock 9.46% 7.88% fio [k]

It was found when running fio sequential write test with a XFS ramdisk on a KVM guest 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] call_rwsem_down_write_failed 67.12% 1.12% fio [k] rwsem_down_write_failed 63.48% 52.77% fio [k] osq_lock 9.46% 7.88% fio [k]

On Fri, Feb 10, 2017 at 12:00:43PM -0500, Waiman Long wrote: > >> +asm( > >> +".pushsection .text;" > >> +".global __raw_callee_save___kvm_vcpu_is_preempted;" > >> +".type __raw_callee_save___kvm_vcpu_is_preempted, @function;" > >> +"__raw_callee_save___kvm_vcpu_is_preempted:" > >> +FRAME_BEGIN >

On Fri, Feb 10, 2017 at 12:00:43PM -0500, Waiman Long wrote: > >> +asm( > >> +".pushsection .text;" > >> +".global __raw_callee_save___kvm_vcpu_is_preempted;" > >> +".type __raw_callee_save___kvm_vcpu_is_preempted, @function;" > >> +"__raw_callee_save___kvm_vcpu_is_preempted:" > >> +FRAME_BEGIN >

It was found when running fio sequential write test with a XFS ramdisk on a 2-socket x86-64 system, the %CPU times as reported by perf were as follows: 71.27% 0.28% fio [k] down_write 70.99% 0.01% fio [k] call_rwsem_down_write_failed 69.43% 1.18% fio [k] rwsem_down_write_failed 65.51% 54.57% fio [k] osq_lock 9.72% 7.99% fio [k] __raw_callee_save___kvm_vcpu_is_preempted 4.16%

It was found when running fio sequential write test with a XFS ramdisk on a 2-socket x86-64 system, the %CPU times as reported by perf were as follows: 71.27% 0.28% fio [k] down_write 70.99% 0.01% fio [k] call_rwsem_down_write_failed 69.43% 1.18% fio [k] rwsem_down_write_failed 65.51% 54.57% fio [k] osq_lock 9.72% 7.99% fio [k] __raw_callee_save___kvm_vcpu_is_preempted 4.16%

On Wed, Nov 02, 2016 at 05:08:33AM -0400, Pan Xinhui wrote: > diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h > index 0f400c0..38c3bb7 100644 > --- a/arch/x86/include/asm/paravirt_types.h > +++ b/arch/x86/include/asm/paravirt_types.h > @@ -310,6 +310,8 @@ struct pv_lock_ops { > > void (*wait)(u8 *ptr, u8 val); > void

On Wed, Nov 02, 2016 at 05:08:33AM -0400, Pan Xinhui wrote: > diff --git a/arch/x86/include/asm/paravirt_types.h b/arch/x86/include/asm/paravirt_types.h > index 0f400c0..38c3bb7 100644 > --- a/arch/x86/include/asm/paravirt_types.h > +++ b/arch/x86/include/asm/paravirt_types.h > @@ -310,6 +310,8 @@ struct pv_lock_ops { > > void (*wait)(u8 *ptr, u8 val); > void

On 02/10/2017 11:35 AM, Waiman Long wrote: > 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: >>> >>>

2016-10-19 06:20-0400, Pan Xinhui: > This is to fix some lock holder preemption issues. Some other locks > implementation do a spin loop before acquiring the lock itself. > Currently kernel has an interface of bool vcpu_is_preempted(int cpu). It > takes the cpu as parameter and return true if the cpu is preempted. Then > kernel can break the spin loops upon on the retval of