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From: Peter Xu <peterx@redhat.com>
To: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	linux-kernel@vger.kernel.org, kvm@vger.kernel.org,
	Sean Christopherson <sean.j.christopherson@intel.com>,
	"Dr . David Alan Gilbert" <dgilbert@redhat.com>,
	Vitaly Kuznetsov <vkuznets@redhat.com>
Subject: Re: [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking
Date: Tue, 10 Dec 2019 11:02:11 -0500
Message-ID: <20191210160211.GE3352@xz-x1> (raw)
In-Reply-To: <8843d1c8-1c87-e789-9930-77e052bf72f9@redhat.com>

On Tue, Dec 10, 2019 at 02:31:54PM +0100, Paolo Bonzini wrote:
> On 10/12/19 14:25, Michael S. Tsirkin wrote:
> >> There is no new infrastructure to track the dirty pages---it's just a
> >> different way to pass them to userspace.
> > Did you guys consider using one of the virtio ring formats?
> > Maybe reusing vhost code?
> 
> There are no used/available entries here, it's unidirectional
> (kernel->user).

Agreed.  Vring could be an overkill IMHO (the whole dirty_ring.c is
100+ LOC only).

> 
> > If you did and it's not a good fit, this is something good to mention
> > in the commit log.
> > 
> > I also wonder about performance numbers - any data here?
> 
> Yes some numbers would be useful.  Note however that the improvement is
> asymptotical, O(#dirtied pages) vs O(#total pages) so it may differ
> depending on the workload.

Yes.  I plan to give some numbers when start to work on the QEMU
series (after this lands).  However as Paolo said, those numbers would
probably only be with some special case where I know the dirty ring
could win.  Frankly speaking I don't even know whether we should
change the default logging mode when the QEMU work is done - I feel
like the old logging interface is still good in many major cases
(small vms, or high dirty rates).  It could be that we just offer
another option when the user could consider to solve specific problems.

Thanks,

-- 
Peter Xu


  reply index

Thread overview: 121+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-29 21:34 [PATCH RFC 00/15] KVM: Dirty ring interface Peter Xu
2019-11-29 21:34 ` [PATCH RFC 01/15] KVM: Move running VCPU from ARM to common code Peter Xu
2019-12-03 19:01   ` Sean Christopherson
2019-12-04  9:42     ` Paolo Bonzini
2019-12-09 22:05       ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 02/15] KVM: Add kvm/vcpu argument to mark_dirty_page_in_slot Peter Xu
2019-12-02 19:32   ` Sean Christopherson
2019-12-02 20:49     ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 03/15] KVM: Add build-time error check on kvm_run size Peter Xu
2019-12-02 19:30   ` Sean Christopherson
2019-12-02 20:53     ` Peter Xu
2019-12-02 22:19       ` Sean Christopherson
2019-12-02 22:40         ` Peter Xu
2019-12-03  5:50           ` Sean Christopherson
2019-12-03 13:41         ` Paolo Bonzini
2019-12-03 17:04           ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 04/15] KVM: Implement ring-based dirty memory tracking Peter Xu
2019-12-02 20:10   ` Sean Christopherson
2019-12-02 21:16     ` Peter Xu
2019-12-02 21:50       ` Sean Christopherson
2019-12-02 23:09         ` Peter Xu
2019-12-03 13:48         ` Paolo Bonzini
2019-12-03 18:46           ` Sean Christopherson
2019-12-04 10:05             ` Paolo Bonzini
2019-12-07  0:29               ` Sean Christopherson
2019-12-09  9:37                 ` Paolo Bonzini
2019-12-09 21:54               ` Peter Xu
2019-12-10 10:07                 ` Paolo Bonzini
2019-12-10 15:52                   ` Peter Xu
2019-12-10 17:09                     ` Paolo Bonzini
2019-12-15 17:21                       ` Peter Xu
2019-12-16 10:08                         ` Paolo Bonzini
2019-12-16 18:54                           ` Peter Xu
2019-12-17  9:01                             ` Paolo Bonzini
2019-12-17 16:24                               ` Peter Xu
2019-12-17 16:28                                 ` Paolo Bonzini
2019-12-18 21:58                                   ` Peter Xu
2019-12-18 22:24                                     ` Sean Christopherson
2019-12-18 22:37                                       ` Paolo Bonzini
2019-12-18 22:49                                         ` Peter Xu
2019-12-17  2:28                           ` Tian, Kevin
2019-12-17 16:18                             ` Alex Williamson
2019-12-17 16:30                               ` Paolo Bonzini
2019-12-18  0:29                                 ` Tian, Kevin
     [not found]                           ` <AADFC41AFE54684AB9EE6CBC0274A5D19D645E5F@SHSMSX104.ccr.corp.intel.com>
2019-12-17  5:17                             ` Tian, Kevin
2019-12-17  5:25                               ` Yan Zhao
2019-12-17 16:24                                 ` Alex Williamson
2019-12-03 19:13   ` Sean Christopherson
2019-12-04 10:14     ` Paolo Bonzini
2019-12-04 14:33       ` Sean Christopherson
2019-12-04 10:38   ` Jason Wang
2019-12-04 11:04     ` Paolo Bonzini
2019-12-04 19:52       ` Peter Xu
2019-12-05  6:51         ` Jason Wang
2019-12-05 12:08           ` Peter Xu
2019-12-05 13:12             ` Jason Wang
2019-12-10 13:25       ` Michael S. Tsirkin
2019-12-10 13:31         ` Paolo Bonzini
2019-12-10 16:02           ` Peter Xu [this message]
2019-12-10 21:53             ` Michael S. Tsirkin
2019-12-11  9:05               ` Paolo Bonzini
2019-12-11 13:04                 ` Michael S. Tsirkin
2019-12-11 14:54                   ` Peter Xu
2019-12-10 21:48           ` Michael S. Tsirkin
2019-12-11 12:53   ` Michael S. Tsirkin
2019-12-11 14:14     ` Paolo Bonzini
2019-12-11 20:59     ` Peter Xu
2019-12-11 22:57       ` Michael S. Tsirkin
2019-12-12  0:08         ` Paolo Bonzini
2019-12-12  7:36           ` Michael S. Tsirkin
2019-12-12  8:12             ` Paolo Bonzini
2019-12-12 10:38               ` Michael S. Tsirkin
2019-12-15 17:33           ` Peter Xu
2019-12-16  9:47             ` Michael S. Tsirkin
2019-12-16 15:07               ` Peter Xu
2019-12-16 15:33                 ` Michael S. Tsirkin
2019-12-16 15:47                   ` Peter Xu
2019-12-11 17:24   ` Christophe de Dinechin
2019-12-13 20:23     ` Peter Xu
2019-12-14  7:57       ` Paolo Bonzini
2019-12-14 16:26         ` Peter Xu
2019-12-16  9:29           ` Paolo Bonzini
2019-12-16 15:26             ` Peter Xu
2019-12-16 15:31               ` Paolo Bonzini
2019-12-16 15:43                 ` Peter Xu
2019-12-17 12:16         ` Christophe de Dinechin
2019-12-17 12:19           ` Paolo Bonzini
2019-12-17 15:38             ` Peter Xu
2019-12-17 16:31               ` Paolo Bonzini
2019-12-17 16:42                 ` Peter Xu
2019-12-17 16:48                   ` Paolo Bonzini
2019-12-17 19:41                     ` Peter Xu
2019-12-18  0:33                       ` Paolo Bonzini
2019-12-18 16:32                         ` Peter Xu
2019-12-18 16:41                           ` Paolo Bonzini
2019-12-20 18:19       ` Peter Xu
2019-11-29 21:34 ` [PATCH RFC 05/15] KVM: Make dirty ring exclusive to dirty bitmap log Peter Xu
2019-11-29 21:34 ` [PATCH RFC 06/15] KVM: Introduce dirty ring wait queue Peter Xu
2019-11-29 21:34 ` [PATCH RFC 07/15] KVM: X86: Implement ring-based dirty memory tracking Peter Xu
2019-11-29 21:34 ` [PATCH RFC 08/15] KVM: selftests: Always clear dirty bitmap after iteration Peter Xu
2019-11-29 21:34 ` [PATCH RFC 09/15] KVM: selftests: Sync uapi/linux/kvm.h to tools/ Peter Xu
2019-11-29 21:35 ` [PATCH RFC 10/15] KVM: selftests: Use a single binary for dirty/clear log test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 11/15] KVM: selftests: Introduce after_vcpu_run hook for dirty " Peter Xu
2019-11-29 21:35 ` [PATCH RFC 12/15] KVM: selftests: Add dirty ring buffer test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 13/15] KVM: selftests: Let dirty_log_test async for dirty ring test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 14/15] KVM: selftests: Add "-c" parameter to dirty log test Peter Xu
2019-11-29 21:35 ` [PATCH RFC 15/15] KVM: selftests: Test dirty ring waitqueue Peter Xu
2019-11-30  8:29 ` [PATCH RFC 00/15] KVM: Dirty ring interface Paolo Bonzini
2019-12-02  2:13   ` Peter Xu
2019-12-03 13:59     ` Paolo Bonzini
2019-12-05 19:30       ` Peter Xu
2019-12-05 19:59         ` Paolo Bonzini
2019-12-05 20:52           ` Peter Xu
2019-12-02 20:21   ` Sean Christopherson
2019-12-02 20:43     ` Peter Xu
2019-12-04 10:39 ` Jason Wang
2019-12-04 19:33   ` Peter Xu
2019-12-05  6:49     ` Jason Wang
2019-12-11 13:41 ` Christophe de Dinechin
2019-12-11 14:16   ` Paolo Bonzini
2019-12-11 17:15     ` Peter Xu

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