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). Paolo
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