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Re: Grant operation batching
- To: Demi Marie Obenour <demi@xxxxxxxxxxxxxxxxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Fri, 20 May 2022 08:24:48 +0200
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- Cc: Xen developer discussion <xen-devel@xxxxxxxxxxxxxxxxxxxx>
- Delivery-date: Fri, 20 May 2022 06:25:02 +0000
- List-id: Xen developer discussion <xen-devel.lists.xenproject.org>
On 20.05.2022 01:22, Demi Marie Obenour wrote:
> It is well known that mapping and unmapping grants is expensive, which
> is why blkback has persistent grants. Could this cost be mitigated by
> batching, and if it was, would it affect the tradeoff of memcpy() vs
> grant table operations?
Which backend driver are you thinking about? The in-kernel Linux
xen-blkback already batches grant operations, afaics. Such
batching is helpful, but the main cost is assumed (known?) to be
with the (installing and) tearing down of the actual mappings of
the guest pages (into/)from backend address space.
Jan
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