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From: Yongji Xie <xieyongji@bytedance.com>
To: Jason Wang <jasowang@redhat.com>, Robin Murphy <robin.murphy@arm.com>
Cc: kvm <kvm@vger.kernel.org>, "Michael S. Tsirkin" <mst@redhat.com>,
	virtualization <virtualization@lists.linux-foundation.org>,
	"Christian Brauner" <christian.brauner@canonical.com>,
	"Jonathan Corbet" <corbet@lwn.net>,
	"Matthew Wilcox" <willy@infradead.org>,
	"Christoph Hellwig" <hch@infradead.org>,
	"Dan Carpenter" <dan.carpenter@oracle.com>,
	"Stefano Garzarella" <sgarzare@redhat.com>,
	"Liu Xiaodong" <xiaodong.liu@intel.com>,
	"Joe Perches" <joe@perches.com>,
	"Al Viro" <viro@zeniv.linux.org.uk>,
	"Stefan Hajnoczi" <stefanha@redhat.com>,
	songmuchun@bytedance.com, "Jens Axboe" <axboe@kernel.dk>,
	"He Zhe" <zhe.he@windriver.com>,
	"Greg KH" <gregkh@linuxfoundation.org>,
	"Randy Dunlap" <rdunlap@infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	iommu@lists.linux-foundation.org, bcrl@kvack.org,
	netdev@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	"Mika Penttilä" <mika.penttila@nextfour.com>
Subject: Re: [PATCH v10 01/17] iova: Export alloc_iova_fast() and free_iova_fast()
Date: Tue, 10 Aug 2021 15:43:56 +0800	[thread overview]
Message-ID: <CACycT3vuBdmWdu4X9wjCO0hm+O0xH2Uf0S2ZTk4O_pL2jX6Y5g@mail.gmail.com> (raw)
In-Reply-To: <b427cf12-2ff6-e5cd-fe6a-3874d8622a29@redhat.com>

On Tue, Aug 10, 2021 at 11:02 AM Jason Wang <jasowang@redhat.com> wrote:
>
>
> 在 2021/8/9 下午1:56, Yongji Xie 写道:
> > On Thu, Aug 5, 2021 at 9:31 PM Jason Wang <jasowang@redhat.com> wrote:
> >>
> >> 在 2021/8/5 下午8:34, Yongji Xie 写道:
> >>>> My main point, though, is that if you've already got something else
> >>>> keeping track of the actual addresses, then the way you're using an
> >>>> iova_domain appears to be something you could do with a trivial bitmap
> >>>> allocator. That's why I don't buy the efficiency argument. The main
> >>>> design points of the IOVA allocator are to manage large address spaces
> >>>> while trying to maximise spatial locality to minimise the underlying
> >>>> pagetable usage, and allocating with a flexible limit to support
> >>>> multiple devices with different addressing capabilities in the same
> >>>> address space. If none of those aspects are relevant to the use-case -
> >>>> which AFAICS appears to be true here - then as a general-purpose
> >>>> resource allocator it's rubbish and has an unreasonably massive memory
> >>>> overhead and there are many, many better choices.
> >>>>
> >>> OK, I get your point. Actually we used the genpool allocator in the
> >>> early version. Maybe we can fall back to using it.
> >>
> >> I think maybe you can share some perf numbers to see how much
> >> alloc_iova_fast() can help.
> >>
> > I did some fio tests[1] with a ram-backend vduse block device[2].
> >
> > Following are some performance data:
> >
> >                              numjobs=1   numjobs=2    numjobs=4   numjobs=8
> > iova_alloc_fast    145k iops      265k iops      514k iops      758k iops
> >
> > iova_alloc            137k iops     170k iops      128k iops      113k iops
> >
> > gen_pool_alloc   143k iops      270k iops      458k iops      521k iops
> >
> > The iova_alloc_fast() has the best performance since we always hit the
> > per-cpu cache. Regardless of the per-cpu cache, the genpool allocator
> > should be better than the iova allocator.
>
>
> I think we see convincing numbers for using iova_alloc_fast() than the
> gen_poll_alloc() (45% improvement on job=8).
>

Yes, so alloc_iova_fast() still seems to be the best choice based on
performance considerations.

Hi Robin, any comments?

Thanks,
Yongji

  reply	other threads:[~2021-08-10  7:44 UTC|newest]

Thread overview: 55+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-07-29  7:34 [PATCH v10 00/17] Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-07-29  7:34 ` [PATCH v10 01/17] iova: Export alloc_iova_fast() and free_iova_fast() Xie Yongji
2021-08-03  7:41   ` Jason Wang
2021-08-03  7:41   ` Jason Wang
2021-08-03  8:54     ` Yongji Xie
2021-08-03 10:53       ` Robin Murphy
2021-08-04  5:02         ` Yongji Xie
2021-08-04 15:43           ` Robin Murphy
2021-08-05 12:34             ` Yongji Xie
2021-08-05 13:31               ` Jason Wang
2021-08-09  5:56                 ` Yongji Xie
2021-08-10  3:02                   ` Jason Wang
2021-08-10  7:43                     ` Yongji Xie [this message]
2021-07-29  7:34 ` [PATCH v10 02/17] file: Export receive_fd() to modules Xie Yongji
2021-08-03  7:45   ` Jason Wang
2021-08-03  9:01     ` Yongji Xie
2021-08-04  8:27       ` Jason Wang
2021-07-29  7:34 ` [PATCH v10 03/17] vdpa: Fix code indentation Xie Yongji
2021-08-03  7:50   ` Jason Wang
2021-08-03  9:13     ` Yongji Xie
2021-07-29  7:34 ` [PATCH v10 04/17] vdpa: Fail the vdpa_reset() if fail to set device status to zero Xie Yongji
2021-08-03  7:58   ` Jason Wang
2021-08-03  9:31     ` Yongji Xie
2021-08-04  8:30       ` Jason Wang
2021-07-29  7:34 ` [PATCH v10 05/17] vhost-vdpa: Fail the vhost_vdpa_set_status() on reset failure Xie Yongji
2021-08-03  8:10   ` Jason Wang
2021-08-03  9:50     ` Yongji Xie
2021-08-04  8:33       ` Jason Wang
2021-07-29  7:34 ` [PATCH v10 06/17] vhost-vdpa: Handle the failure of vdpa_reset() Xie Yongji
2021-07-29  7:34 ` [PATCH v10 07/17] virtio: Don't set FAILED status bit on device index allocation failure Xie Yongji
2021-08-03  8:02   ` Jason Wang
2021-08-03  9:17     ` Yongji Xie
2021-07-29  7:34 ` [PATCH v10 08/17] virtio_config: Add a return value to reset function Xie Yongji
2021-07-29  7:34 ` [PATCH v10 09/17] virtio-vdpa: Handle the failure of vdpa_reset() Xie Yongji
2021-07-29  7:34 ` [PATCH v10 10/17] virtio: Handle device reset failure in register_virtio_device() Xie Yongji
2021-08-03  8:09   ` Jason Wang
2021-08-03  9:38     ` Yongji Xie
2021-08-04  8:32       ` Jason Wang
2021-08-04  8:50         ` Yongji Xie
2021-08-04  8:54           ` Jason Wang
2021-08-04  9:07             ` Yongji Xie
2021-08-05  7:12               ` Jason Wang
2021-07-29  7:34 ` [PATCH v10 11/17] vhost-iotlb: Add an opaque pointer for vhost IOTLB Xie Yongji
2021-07-29  7:34 ` [PATCH v10 12/17] vdpa: Add an opaque pointer for vdpa_config_ops.dma_map() Xie Yongji
2021-07-29  7:34 ` [PATCH v10 13/17] vdpa: factor out vhost_vdpa_pa_map() and vhost_vdpa_pa_unmap() Xie Yongji
2021-07-29  7:35 ` [PATCH v10 14/17] vdpa: Support transferring virtual addressing during DMA mapping Xie Yongji
2021-07-29  7:35 ` [PATCH v10 15/17] vduse: Implement an MMU-based software IOTLB Xie Yongji
2021-07-29  7:35 ` [PATCH v10 16/17] vduse: Introduce VDUSE - vDPA Device in Userspace Xie Yongji
2021-07-29  9:00   ` Greg KH
2021-07-29  9:57     ` Yongji Xie
2021-08-03  7:30   ` Jason Wang
2021-08-03  8:39     ` Yongji Xie
2021-07-29  7:35 ` [PATCH v10 17/17] Documentation: Add documentation for VDUSE Xie Yongji
2021-08-03  7:35   ` Jason Wang
2021-08-03  8:52     ` Yongji Xie

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