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Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_m
From: |
Paolo Bonzini |
Subject: |
Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap |
Date: |
Tue, 11 Jul 2017 12:28:14 +0200 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 |
On 11/07/2017 12:05, Stefan Hajnoczi wrote:
> On Mon, Jul 10, 2017 at 05:08:56PM +0200, Paolo Bonzini wrote:
>> On 10/07/2017 17:07, Stefan Hajnoczi wrote:
>>> On Wed, Jul 05, 2017 at 09:36:32PM +0800, Fam Zheng wrote:
>>>> Allow block driver to map and unmap a buffer for later I/O, as a
>>>> performance
>>>> hint.
>>> The name blk_dma_map() is confusing since other "dma" APIs like
>>> dma_addr_t and dma_blk_io() deal with guest physical addresses instead
>>> of host addresses. They are about DMA to/from guest RAM.
>>>
>>> Have you considered hiding this cached mapping in block/nvme.c so that
>>> it isn't exposed? block/nvme.c could keep the last buffer mapped and
>>> callers would get the performance benefit without a new blk_dma_map()
>>> API.
>>
>> One buffer is enough for qemu-img bench, but not for more complex cases
>> (e.g. fio).
>
> I don't see any other blk_dma_map() callers.
Indeed, the fio plugin is not part of this series, but it also used
blk_dma_map. Without it, performance is awful.
Paolo
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- [Qemu-devel] [PATCH v3 0/6] block: Add VFIO based driver for NVMe device, Fam Zheng, 2017/07/05
- [Qemu-devel] [PATCH v3 1/6] stubs: Add stubs for ram block API, Fam Zheng, 2017/07/05
- [Qemu-devel] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Fam Zheng, 2017/07/05
- Re: [Qemu-devel] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Stefan Hajnoczi, 2017/07/10
- Re: [Qemu-devel] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Stefan Hajnoczi, 2017/07/10
- Re: [Qemu-devel] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Paolo Bonzini, 2017/07/10
- Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Stefan Hajnoczi, 2017/07/11
- Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap,
Paolo Bonzini <=
- Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Fam Zheng, 2017/07/11
- Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Paolo Bonzini, 2017/07/12
- Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Stefan Hajnoczi, 2017/07/14
- Re: [Qemu-devel] [Qemu-block] [PATCH v3 3/6] block: Introduce bdrv_dma_map and bdrv_dma_unmap, Paolo Bonzini, 2017/07/14
[Qemu-devel] [PATCH v3 2/6] block: Add VFIO based NVMe driver, Fam Zheng, 2017/07/05