search for: yield_to

...g for kicking the lock holder. > > I agree. If the lock holder isn't running, there's probably a good > reason for that and going to sleep will not necessarily convince the > scheduler to give more CPU to the lock holder. I think there are two > choices: > > 1) use yield_to to donate part of the waiter's quantum to the lock > holder? For this we probably need a new, separate hypercall > interface. For KVM it would be the same as hlt in the guest but with > an additional yield_to in the host. > > 2) do nothing, just go to sleep. > > Coul...

...g for kicking the lock holder. > > I agree. If the lock holder isn't running, there's probably a good > reason for that and going to sleep will not necessarily convince the > scheduler to give more CPU to the lock holder. I think there are two > choices: > > 1) use yield_to to donate part of the waiter's quantum to the lock > holder? For this we probably need a new, separate hypercall > interface. For KVM it would be the same as hlt in the guest but with > an additional yield_to in the host. > > 2) do nothing, just go to sleep. > > Coul...

On 12/03/14 18:54, Waiman Long wrote: > This patch adds para-virtualization support to the queue spinlock in > the same way as was done in the PV ticket lock code. In essence, the > lock waiters will spin for a specified number of times (QSPIN_THRESHOLD > = 2^14) and then halted itself. The queue head waiter will spins > 2*QSPIN_THRESHOLD times before halting itself. When it has

On 12/03/14 18:54, Waiman Long wrote: > This patch adds para-virtualization support to the queue spinlock in > the same way as was done in the PV ticket lock code. In essence, the > lock waiters will spin for a specified number of times (QSPIN_THRESHOLD > = 2^14) and then halted itself. The queue head waiter will spins > 2*QSPIN_THRESHOLD times before halting itself. When it has

...;t really understand the reasoning for kicking the lock holder. I agree. If the lock holder isn't running, there's probably a good reason for that and going to sleep will not necessarily convince the scheduler to give more CPU to the lock holder. I think there are two choices: 1) use yield_to to donate part of the waiter's quantum to the lock holder? For this we probably need a new, separate hypercall interface. For KVM it would be the same as hlt in the guest but with an additional yield_to in the host. 2) do nothing, just go to sleep. Could you get (or do you have) number...

.../0xf0 [nouveau] [ 9.979924] nvkm_object_init+0x6a/0x2e0 [nouveau] [ 9.984932] nvkm_ioctl_new+0x198/0x430 [nouveau] [ 9.989846] ? nvif_vmm_init+0x340/0x340 [nouveau] [ 9.994864] ? nvkm_udevice_rd08+0x90/0x90 [nouveau] [ 10.000056] nvkm_ioctl+0x21e/0x5a0 [nouveau] [ 10.004548] ? yield_to+0x2b2/0x370 [ 10.008257] nvif_object_init+0xef/0x1b0 [nouveau] [ 10.013281] nvif_device_init+0x9/0x40 [nouveau] [ 10.018136] nouveau_cli_init+0x234/0x12f0 [nouveau] [ 10.023253] ? idr_alloc_cyclic+0x6c/0x110 [ 10.027487] ? _cond_resched+0x1d/0x80 [ 10.031366] ? kmem_cache_alloc+0x...

...my proposal boils down to: - lowest latency: use barrier() or mb() if necessary - low latency: use cpu_relax (e.g. might give up some cpu for the other _hardware_ threads) - really give up CPU: use cpu_relax_yield PS: In the long run I would also try to provide for s390 something like cpu_relax_yield_to with a cpu number (or just add that to cpu_relax_yield), since a yield_to is always better than a yield as long as we know the waiter. ---------------------------------------------------------------- Christian Borntraeger (5): processor.h: introduce cpu_relax_yield stop_machine: yield...

...my proposal boils down to: - lowest latency: use barrier() or mb() if necessary - low latency: use cpu_relax (e.g. might give up some cpu for the other _hardware_ threads) - really give up CPU: use cpu_relax_yield PS: In the long run I would also try to provide for s390 something like cpu_relax_yield_to with a cpu number (or just add that to cpu_relax_yield), since a yield_to is always better than a yield as long as we know the waiter. ---------------------------------------------------------------- Christian Borntraeger (5): processor.h: introduce cpu_relax_yield stop_machine: yield...