Re: [Qemu-devel] [PATCH v3 1/7] block: use 1 MB bounce buffers for crypto instead of 16KB

[Max Reitz]

On 2017-09-12 13:28, Daniel P. Berrange wrote:
> Using 16KB bounce buffers creates a significant performance
> penalty for I/O to encrypted volumes on storage which high
> I/O latency (rotating rust & network drives), because it
> triggers lots of fairly small I/O operations.
> 
> On tests with rotating rust, and cache=none|directsync,
> write speed increased from 2MiB/s to 32MiB/s, on a par
> with that achieved by the in-kernel luks driver. With
> other cache modes the in-kernel driver is still notably
> faster because it is able to report completion of the
> I/O request before any encryption is done, while the
> in-QEMU driver must encrypt the data before completion.
> 
> Reviewed-by: Eric Blake <address@hidden>
> Reviewed-by: Stefan Hajnoczi <address@hidden>
> Signed-off-by: Daniel P. Berrange <address@hidden>
> ---
>  block/crypto.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)

Reviewed-by: Max Reitz <address@hidden>

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