Re: [Xen-devel] [PATCH v10 4/5] remus: implement remus network buffering for nic devices

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Shriram Rajagopalan writes ("Re: [PATCH v10 4/5] remus: implement remus network 
buffering for nic devices"):
...
> The async execution for each netlink call is an overkill.  These
> rtnl calls complete in a matter of few microseconds utmost. On the
> other hand, this code structure, fork/execs a new process for every
> checkpoint just to execute a single library call (netbuf_epoch_op),
> which in turn issues just a syscall.

I haven't read the code to check whether this criticism is accurate,
but if it is I think it would be justified.

There is no need to use the async machinery for fast system calls.

> Correct me if I am wrong. I am assuming that the
> libxl__ev_child_fork eventually leads to a fork() and exec() call.

libxl__ev_child_fork leads to a fork() but not necessarily an exec().
The libxl code which uses it is supposed to make the child either exec
soon, or exit soon.  ("Soon" is defined in more detail in the doc
comment.)

If in fact the proposed patch forks/execs a netlink tool for each
checkpoint, it would probably be better for it to make the relevant
netlink calls directly.

Ian.

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