From: "Michael S. Tsirkin" <mst@redhat.com>
To: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Cc: robh@kernel.org, srikar@linux.vnet.ibm.com, aik@ozlabs.ru,
jasowang@redhat.com, linuxram@us.ibm.com,
linux-kernel@vger.kernel.org,
virtualization@lists.linux-foundation.org, hch@infradead.org,
paulus@samba.org, joe@perches.com, linuxppc-dev@lists.ozlabs.org,
elfring@users.sourceforge.net, haren@linux.vnet.ibm.com,
david@gibson.dropbear.id.au
Subject: Re: [RFC 0/4] Virtio uses DMA API for all devices
Date: Mon, 23 Jul 2018 12:08:42 +0300 [thread overview]
Message-ID: <20180723120511-mutt-send-email-mst@kernel.org> (raw)
In-Reply-To: <8f51d2c6-cc0c-9e42-f0fd-a8a33acc8b83@linux.vnet.ibm.com>
On Mon, Jul 23, 2018 at 11:58:23AM +0530, Anshuman Khandual wrote:
> On 07/20/2018 06:46 PM, Michael S. Tsirkin wrote:
> > On Fri, Jul 20, 2018 at 09:29:37AM +0530, Anshuman Khandual wrote:
> >> This patch series is the follow up on the discussions we had before about
> >> the RFC titled [RFC,V2] virtio: Add platform specific DMA API translation
> >> for virito devices (https://patchwork.kernel.org/patch/10417371/). There
> >> were suggestions about doing away with two different paths of transactions
> >> with the host/QEMU, first being the direct GPA and the other being the DMA
> >> API based translations.
> >>
> >> First patch attempts to create a direct GPA mapping based DMA operations
> >> structure called 'virtio_direct_dma_ops' with exact same implementation
> >> of the direct GPA path which virtio core currently has but just wrapped in
> >> a DMA API format. Virtio core must use 'virtio_direct_dma_ops' instead of
> >> the arch default in absence of VIRTIO_F_IOMMU_PLATFORM flag to preserve the
> >> existing semantics. The second patch does exactly that inside the function
> >> virtio_finalize_features(). The third patch removes the default direct GPA
> >> path from virtio core forcing it to use DMA API callbacks for all devices.
> >> Now with that change, every device must have a DMA operations structure
> >> associated with it. The fourth patch adds an additional hook which gives
> >> the platform an opportunity to do yet another override if required. This
> >> platform hook can be used on POWER Ultravisor based protected guests to
> >> load up SWIOTLB DMA callbacks to do the required (as discussed previously
> >> in the above mentioned thread how host is allowed to access only parts of
> >> the guest GPA range) bounce buffering into the shared memory for all I/O
> >> scatter gather buffers to be consumed on the host side.
> >>
> >> Please go through these patches and review whether this approach broadly
> >> makes sense. I will appreciate suggestions, inputs, comments regarding
> >> the patches or the approach in general. Thank you.
> > I like how patches 1-3 look. Could you test performance
> > with/without to see whether the extra indirection through
> > use of DMA ops causes a measurable slow-down?
>
> I ran this simple DD command 10 times where /dev/vda is a virtio block
> device of 10GB size.
>
> dd if=/dev/zero of=/dev/vda bs=8M count=1024 oflag=direct
>
> With and without patches bandwidth which has a bit wide range does not
> look that different from each other.
>
> Without patches
> ===============
>
> ---------- 1 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.95557 s, 4.4 GB/s
> ---------- 2 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.05176 s, 4.2 GB/s
> ---------- 3 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.88314 s, 4.6 GB/s
> ---------- 4 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.84899 s, 4.6 GB/s
> ---------- 5 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 5.37184 s, 1.6 GB/s
> ---------- 6 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.9205 s, 4.5 GB/s
> ---------- 7 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 6.85166 s, 1.3 GB/s
> ---------- 8 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.74049 s, 4.9 GB/s
> ---------- 9 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 6.31699 s, 1.4 GB/s
> ---------- 10 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.47057 s, 3.5 GB/s
>
>
> With patches
> ============
>
> ---------- 1 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.25993 s, 3.8 GB/s
> ---------- 2 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.82438 s, 4.7 GB/s
> ---------- 3 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.93856 s, 4.4 GB/s
> ---------- 4 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.83405 s, 4.7 GB/s
> ---------- 5 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 7.50199 s, 1.1 GB/s
> ---------- 6 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.28742 s, 3.8 GB/s
> ---------- 7 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 5.74958 s, 1.5 GB/s
> ---------- 8 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 1.99149 s, 4.3 GB/s
> ---------- 9 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 5.67647 s, 1.5 GB/s
> ---------- 10 ---------
> 1024+0 records in
> 1024+0 records out
> 8589934592 bytes (8.6 GB, 8.0 GiB) copied, 2.93957 s, 2.9 GB/s
>
> Does this look okay ?
You want to test IOPS with lots of small writes and using
raw ramdisk on host.
--
MST
next prev parent reply other threads:[~2018-07-23 9:08 UTC|newest]
Thread overview: 119+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-07-20 3:59 [RFC 0/4] Virtio uses DMA API for all devices Anshuman Khandual
2018-07-20 3:59 ` [RFC 1/4] virtio: Define virtio_direct_dma_ops structure Anshuman Khandual
2018-07-30 9:24 ` Christoph Hellwig
2018-07-31 4:01 ` Anshuman Khandual
2018-07-20 3:59 ` [RFC 2/4] virtio: Override device's DMA OPS with virtio_direct_dma_ops selectively Anshuman Khandual
2018-07-28 8:56 ` Anshuman Khandual
2018-07-28 21:16 ` Michael S. Tsirkin
2018-07-30 4:15 ` Anshuman Khandual
2018-07-30 9:30 ` Christoph Hellwig
2018-07-31 6:39 ` Anshuman Khandual
2018-07-30 9:25 ` Christoph Hellwig
2018-07-31 7:00 ` Anshuman Khandual
2018-07-20 3:59 ` [RFC 3/4] virtio: Force virtio core to use DMA API callbacks for all virtio devices Anshuman Khandual
2018-07-20 3:59 ` [RFC 4/4] virtio: Add platform specific DMA API translation for virito devices Anshuman Khandual
2018-07-20 13:15 ` Michael S. Tsirkin
2018-07-23 2:16 ` Anshuman Khandual
2018-07-25 4:30 ` Anshuman Khandual
2018-07-25 13:31 ` Michael S. Tsirkin
2018-07-20 13:16 ` [RFC 0/4] Virtio uses DMA API for all devices Michael S. Tsirkin
2018-07-23 6:28 ` Anshuman Khandual
2018-07-23 9:08 ` Michael S. Tsirkin [this message]
2018-07-25 3:26 ` Anshuman Khandual
2018-07-27 11:31 ` Michael S. Tsirkin
2018-07-28 8:37 ` Anshuman Khandual
2018-07-27 9:58 ` Will Deacon
2018-07-27 10:58 ` Anshuman Khandual
2018-07-30 9:34 ` Christoph Hellwig
2018-07-30 10:28 ` Michael S. Tsirkin
2018-07-30 11:18 ` Christoph Hellwig
2018-07-30 13:26 ` Michael S. Tsirkin
2018-07-31 17:30 ` Christoph Hellwig
2018-07-31 20:36 ` Benjamin Herrenschmidt
2018-08-01 8:16 ` Will Deacon
2018-08-01 8:36 ` Christoph Hellwig
2018-08-01 9:05 ` Will Deacon
2018-08-01 22:41 ` Michael S. Tsirkin
2018-08-01 22:35 ` Michael S. Tsirkin
2018-08-02 15:24 ` Benjamin Herrenschmidt
2018-08-02 15:41 ` Michael S. Tsirkin
2018-08-02 16:01 ` Benjamin Herrenschmidt
2018-08-02 17:19 ` Michael S. Tsirkin
2018-08-02 17:53 ` Benjamin Herrenschmidt
2018-08-02 20:52 ` Michael S. Tsirkin
2018-08-02 21:13 ` Benjamin Herrenschmidt
2018-08-02 21:51 ` Michael S. Tsirkin
2018-08-03 7:05 ` Christoph Hellwig
2018-08-03 15:58 ` Benjamin Herrenschmidt
2018-08-03 16:02 ` Christoph Hellwig
2018-08-03 18:58 ` Benjamin Herrenschmidt
2018-08-04 8:21 ` Christoph Hellwig
2018-08-05 1:10 ` Benjamin Herrenschmidt
2018-08-05 7:29 ` Christoph Hellwig
2018-08-05 21:16 ` Benjamin Herrenschmidt
2018-08-05 21:30 ` Benjamin Herrenschmidt
2018-08-06 9:42 ` Christoph Hellwig
2018-08-06 19:52 ` Benjamin Herrenschmidt
2018-08-07 6:21 ` Christoph Hellwig
2018-08-07 6:42 ` Benjamin Herrenschmidt
2018-08-07 13:55 ` Christoph Hellwig
2018-08-07 20:32 ` Benjamin Herrenschmidt
2018-08-08 6:31 ` Christoph Hellwig
2018-08-08 10:07 ` Benjamin Herrenschmidt
2018-08-08 12:30 ` Christoph Hellwig
2018-08-08 13:18 ` Benjamin Herrenschmidt
2018-08-08 20:31 ` Michael S. Tsirkin
2018-08-08 22:13 ` Benjamin Herrenschmidt
2018-08-09 2:00 ` Benjamin Herrenschmidt
2018-08-09 5:40 ` Christoph Hellwig
2018-09-07 0:09 ` Jiandi An
2018-09-10 6:19 ` Christoph Hellwig
2018-09-10 8:53 ` Gerd Hoffmann
2018-08-03 19:07 ` Michael S. Tsirkin
2018-08-04 1:11 ` Benjamin Herrenschmidt
2018-08-04 1:16 ` Benjamin Herrenschmidt
2018-08-05 0:22 ` Michael S. Tsirkin
2018-08-05 4:52 ` Benjamin Herrenschmidt
2018-08-06 13:46 ` Michael S. Tsirkin
2018-08-06 19:56 ` Benjamin Herrenschmidt
2018-08-06 20:35 ` Michael S. Tsirkin
2018-08-06 21:26 ` Benjamin Herrenschmidt
2018-08-06 21:46 ` Michael S. Tsirkin
2018-08-06 22:13 ` Benjamin Herrenschmidt
2018-08-06 23:16 ` Benjamin Herrenschmidt
2018-08-06 23:45 ` Michael S. Tsirkin
2018-08-07 0:18 ` Benjamin Herrenschmidt
2018-08-07 6:32 ` Christoph Hellwig
2018-08-07 6:27 ` Christoph Hellwig
2018-08-07 6:44 ` Benjamin Herrenschmidt
2018-08-07 6:18 ` Christoph Hellwig
2018-08-07 6:16 ` Christoph Hellwig
2018-08-06 23:18 ` Benjamin Herrenschmidt
2018-08-07 6:12 ` Christoph Hellwig
2018-08-04 1:18 ` Benjamin Herrenschmidt
2018-08-04 1:22 ` Benjamin Herrenschmidt
2018-08-05 0:23 ` Michael S. Tsirkin
2018-08-03 19:17 ` Michael S. Tsirkin
2018-08-04 8:15 ` Christoph Hellwig
2018-08-05 0:09 ` Michael S. Tsirkin
2018-08-05 1:11 ` Benjamin Herrenschmidt
2018-08-05 7:25 ` Christoph Hellwig
2018-08-05 0:53 ` Benjamin Herrenschmidt
2018-08-05 0:27 ` Michael S. Tsirkin
2018-08-06 14:05 ` Will Deacon
2018-08-01 21:56 ` Michael S. Tsirkin
2018-08-02 15:33 ` Benjamin Herrenschmidt
2018-08-02 20:53 ` Michael S. Tsirkin
2018-08-03 7:06 ` Christoph Hellwig
2018-08-02 20:55 ` Michael S. Tsirkin
2018-08-03 2:41 ` Jason Wang
2018-08-03 19:08 ` Michael S. Tsirkin
2018-08-04 1:21 ` Benjamin Herrenschmidt
2018-08-05 0:24 ` Michael S. Tsirkin
2018-08-06 9:02 ` Anshuman Khandual
2018-08-06 13:36 ` Michael S. Tsirkin
2018-08-06 15:24 ` Christoph Hellwig
2018-08-06 16:06 ` Michael S. Tsirkin
2018-08-06 16:10 ` Christoph Hellwig
2018-08-06 16:13 ` Michael S. Tsirkin
2018-08-06 16:34 ` Christoph Hellwig
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