Does FreeBSD have sendmmsg or recvmmsg system calls?

[Luigi Rizzo]

Hi Boris,
thanks for working on this.

A few comments:

- do you have any performance data on calling *mmsg() versus
  multiple invocations of the equivalent *msg() ?

- in the following chunk in recvmmsg.c , there are slight
  type differences between the function and the internal cast.
  Same in sendmmsg.c

    +ssize_t
    +recvmmsg(int s, struct mmsghdr *msgvec, unsigned int vlen, int flags)
    +{
    +
    +       return (((int (*)(int, struct mmsghdr *, int, int))
    +           __libc_interposing[INTERPOS_recvmmsg])(s, msgvec, vlen, flags));
    +}


- why did you add a cap_rights_init() to the functions when
  neither sendmsg or recvmsg have it (in other words, this is
  a worthwhile addition but perhaps should be done later

- the initial part of the two functions sys_*mmsg() is almost
  exactly the same so can you define a function with the common code ?

- you could probably avoid the repeated malloc/free of the iov
  with a first loop that finds the max iov size and does the allocation
  only once. copyiniov can then be replaced by a copyin

- (minor) what is the point of copying the current entry into msg rather than
  just using mp-> ...

- can you add a comment explaining why you do the following

               error = copyout(&td->td_retval[0], &uap->msgvec[i].msg_len,
                   sizeof(td->td_retval[0]));


cheers
luigi

On Thu, Jan 7, 2016 at 1:51 AM, Boris Astardzhiev
<boris.astardzhiev at gmail.com> wrote:
> Hello,
>
> Here's my implementation of the two system calls. The patch is against HEAD
> from a couple of days:
> commit ff9e83788d7ed52342dcba4dff1e62fdf3cc985c
> Author: ngie <ngie at FreeBSD.org>
> Date:   Mon Jan 4 03:34:22 2016 +0000
>
>     Remove free'ing of an uninitialized variable
>
>     Just remove it completely from the test as it's initialized but unused
> apart
>     from the free(3) call
>
>     Differential Revision: https://reviews.freebsd.org/D4769 (part of
> larger diff)
>     MFC after: 5 days
>     Reported by: cppcheck
>     Reviewed by: oshogbo
>     Sponsored by: EMC / Isilon Storage Division
>
> I've made brief tests using the examples in the manpages in Linux skipping
> the timeout stuff:
> http://man7.org/linux/man-pages/man2/sendmmsg.2.html
> http://man7.org/linux/man-pages/man2/recvmmsg.2.html
>
> I've tried to stick to the comments in the thread but any
> suggestions/testings
> are also welcomed so that I can fix the calls accordingly.
>
> Regards,
> Boris Astardzhiev
>
>
> On Mon, Jan 4, 2016 at 11:07 PM, Mark Delany <c2h at romeo.emu.st> wrote:
>
>> > You just repeat arguments for the text in my messages, which you removed
>> > on reply.
>>
>> My goal is to get you to scruitinize.
>>
>> Thank you for helping.
>>
>>
>> Mark.
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