Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
On 12/03/2010 04:50 PM, Rik van Riel wrote: On 12/02/2010 08:18 PM, Chris Wright wrote: * Rik van Riel (r...@redhat.com) wrote: Keep track of which task is running a KVM vcpu. This helps us figure out later what task to wake up if we want to boost a vcpu that got preempted. Unfortunately there are no guarantees that the same task always keeps the same vcpu, so we can only track the task across a single run of the vcpu. So shouldn't it confine to KVM_RUN? The other vcpu_load callers aren't always a vcpu in a useful runnable state. Yeah, probably. If you want I can move the setting of vcpu-task to kvm_vcpu_ioctl. No need, it's not like something bad will happen. What I'd really like to see is a soft binding between a vcpu and its thread, so directed yield works even if we're in qemu while we were scheduled out. In fact it's not an unlikely pattern: spin_lock(lock) ... writel(some_port_handled_by_qemu) ... spin_unlock(lock) but that can wait. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
On 12/03/2010 04:16 PM, Rik van Riel wrote: On 12/03/2010 07:17 AM, Srivatsa Vaddagiri wrote: On Thu, Dec 02, 2010 at 02:43:24PM -0500, Rik van Riel wrote: mutex_lock(vcpu-mutex); +vcpu-task = current; Shouldn't we grab reference to current task_struct before storing a pointer to it? That should not be needed, since current cannot go away without setting vcpu-task back to NULL in vcpu_put. However, you do reference vcpu-task from other contexts. So some sort of safe reference is needed. -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
On Thu, Dec 02, 2010 at 02:43:24PM -0500, Rik van Riel wrote: mutex_lock(vcpu-mutex); + vcpu-task = current; Shouldn't we grab reference to current task_struct before storing a pointer to it? - vatsa -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
On 12/03/2010 07:17 AM, Srivatsa Vaddagiri wrote: On Thu, Dec 02, 2010 at 02:43:24PM -0500, Rik van Riel wrote: mutex_lock(vcpu-mutex); + vcpu-task = current; Shouldn't we grab reference to current task_struct before storing a pointer to it? That should not be needed, since current cannot go away without setting vcpu-task back to NULL in vcpu_put. -- All rights reversed -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
On 12/02/2010 08:18 PM, Chris Wright wrote: * Rik van Riel (r...@redhat.com) wrote: Keep track of which task is running a KVM vcpu. This helps us figure out later what task to wake up if we want to boost a vcpu that got preempted. Unfortunately there are no guarantees that the same task always keeps the same vcpu, so we can only track the task across a single run of the vcpu. So shouldn't it confine to KVM_RUN? The other vcpu_load callers aren't always a vcpu in a useful runnable state. Yeah, probably. If you want I can move the setting of vcpu-task to kvm_vcpu_ioctl. -- All rights reversed -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
* Rik van Riel (r...@redhat.com) wrote: On 12/02/2010 08:18 PM, Chris Wright wrote: * Rik van Riel (r...@redhat.com) wrote: Keep track of which task is running a KVM vcpu. This helps us figure out later what task to wake up if we want to boost a vcpu that got preempted. Unfortunately there are no guarantees that the same task always keeps the same vcpu, so we can only track the task across a single run of the vcpu. So shouldn't it confine to KVM_RUN? The other vcpu_load callers aren't always a vcpu in a useful runnable state. Yeah, probably. If you want I can move the setting of vcpu-task to kvm_vcpu_ioctl. Or maybe setting in sched_out and unsetting in sched_in. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC PATCH 1/3] kvm: keep track of which task is running a KVM vcpu
* Rik van Riel (r...@redhat.com) wrote: Keep track of which task is running a KVM vcpu. This helps us figure out later what task to wake up if we want to boost a vcpu that got preempted. Unfortunately there are no guarantees that the same task always keeps the same vcpu, so we can only track the task across a single run of the vcpu. So shouldn't it confine to KVM_RUN? The other vcpu_load callers aren't always a vcpu in a useful runnable state. -- To unsubscribe from this list: send the line unsubscribe kvm in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
