Re: [PATCH] vhost-net: utilize PUBLISH_USED_IDX feature
On 05/20/2010 01:27 AM, Michael S. Tsirkin wrote: On Wed, May 19, 2010 at 08:04:51PM +0300, Avi Kivity wrote: On 05/18/2010 04:19 AM, Michael S. Tsirkin wrote: With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkinm...@redhat.com --- Rusty, Dave, this patch depends on the patch virtio: put last seen used index into ring itself which is currently destined at Rusty's tree. Rusty, if you are taking that one for 2.6.35, please take this one as well. Dave, any objections? I object: I think the index should have its own cacheline, The issue here is that host/guest do not know each other's cache line size. I guess we could just put it at offset 128 or something like that ... Rusty? Not so pretty, but ok. and that it should be documented before merging. I think you meant to object to the virtio patch, not this one. This patch does not introduce new layout, just implements host support. virtio spec patch will follow: it is not part of linux tree so there is no patch dependency. There is a reviewer dependency. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- 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: [PATCH] vhost-net: utilize PUBLISH_USED_IDX feature
On 05/18/2010 04:19 AM, Michael S. Tsirkin wrote: With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkinm...@redhat.com --- Rusty, Dave, this patch depends on the patch virtio: put last seen used index into ring itself which is currently destined at Rusty's tree. Rusty, if you are taking that one for 2.6.35, please take this one as well. Dave, any objections? I object: I think the index should have its own cacheline, and that it should be documented before merging. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- 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: [PATCH] vhost-net: utilize PUBLISH_USED_IDX feature
On Wed, May 19, 2010 at 08:04:51PM +0300, Avi Kivity wrote: On 05/18/2010 04:19 AM, Michael S. Tsirkin wrote: With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkinm...@redhat.com --- Rusty, Dave, this patch depends on the patch virtio: put last seen used index into ring itself which is currently destined at Rusty's tree. Rusty, if you are taking that one for 2.6.35, please take this one as well. Dave, any objections? I object: I think the index should have its own cacheline, The issue here is that host/guest do not know each other's cache line size. I guess we could just put it at offset 128 or something like that ... Rusty? and that it should be documented before merging. I think you meant to object to the virtio patch, not this one. This patch does not introduce new layout, just implements host support. virtio spec patch will follow: it is not part of linux tree so there is no patch dependency. -- Do not meddle in the internals of kernels, for they are subtle and quick to panic. -- 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: [PATCH] vhost-net: utilize PUBLISH_USED_IDX feature
On Thu, 20 May 2010 07:57:18 am Michael S. Tsirkin wrote: On Wed, May 19, 2010 at 08:04:51PM +0300, Avi Kivity wrote: On 05/18/2010 04:19 AM, Michael S. Tsirkin wrote: With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkinm...@redhat.com --- Rusty, Dave, this patch depends on the patch virtio: put last seen used index into ring itself which is currently destined at Rusty's tree. Rusty, if you are taking that one for 2.6.35, please take this one as well. Dave, any objections? I object: I think the index should have its own cacheline, The issue here is that host/guest do not know each other's cache line size. I guess we could just put it at offset 128 or something like that ... Rusty? I was assuming you'd put it at the end of the padding. I think it's a silly optimization, but Avi obviously feels strongly about it and I respect his opinion. Please resubmit... Thanks, Rusty. -- 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: [PATCH] vhost-net: utilize PUBLISH_USED_IDX feature
From: Michael S. Tsirkin m...@redhat.com Date: Tue, 18 May 2010 04:19:31 +0300 With PUBLISH_USED_IDX, guest tells us which used entries it has consumed. This can be used to reduce the number of interrupts: after we write a used entry, if the guest has not yet consumed the previous entry, or if the guest has already consumed the new entry, we do not need to interrupt. This imporves bandwidth by 30% under some workflows. Signed-off-by: Michael S. Tsirkin m...@redhat.com --- Rusty, Dave, this patch depends on the patch virtio: put last seen used index into ring itself which is currently destined at Rusty's tree. Rusty, if you are taking that one for 2.6.35, please take this one as well. Dave, any objections? None: Acked-by: David S. Miller da...@davemloft.net -- 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
