Zero copy data transfer from Linuxulator to FreeBSD?

[Lundberg, Johannes]

Hi Hans

I created a unix socket and increased send buffer to 1 MB to avoid partial
transfers (not sure how much of a benefit there is of that though).
It seems to running very nicely. Not stalls or anything like a couple of
years ago.


On Sat, Apr 2, 2016 at 2:22 AM, Hans Petter Selasky <hps at selasky.org> wrote:

> On 04/01/16 17:18, Lundberg, Johannes wrote:
>
>> Hi Luigi
>>
>> Since this is an embedded device running on battery every bit counts.
>> However, this is kind of a temporary solution so I'm considering accepting
>> it..
>>
>> At any rate, I am generally curious what mechanism there are for
>> transferring data between Linux and native process in FreeBSD..
>>
>>
> Hi,
>
> libusb has only one copy to/from userspace. libusb v1.0 and v0.1 has some
> allocation during operation, while libusb v2.0 API doesn't.
>
> There was an optimisation done recently about IOCTLs allocating memory for
> the data argument. Maybe that is what is causing the problem you saw?
>
> Refer to SYS_IOCTL_SMALL_SIZE in sys/kern/ .
>
> --HPS
>
>

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