Patrick McHardy wrote:
Ariane Keller wrote:
Thanks for your comments!
I'd like to better understand your dislike of the current
implementation of the data transfer from user space to kernel space.
Is it the fact that we use configfs?
I think, we had already a discussion about this (and we changed from
procfs to configfs).
Or don't you like that we need a user space daemon which is
responsible for feeding the data to the kernel module?
I think we do not have another option, since the trace file may be of
arbitrary length.
Or anything else?
I dislike using anything besides rtnetlink for qdisc configuration.
The only way to transfer arbitary amounts of data over netlink would
be to spread the data over multiple messages. But then again, you're
using kmalloc and only seem to allocate 4k, so how large are these
traces in practice?
For each packet to be processed there is 32bit of data, which encodes
delay and drop, duplicate etc. The size of the actual trace file can
therefore reach any length, depending on for how many packets the
information is encoded (up to several GB).
Therefore we send the trace file in chunks of 4000bytes to the kernel.
In order to have always a "packet-delay-value ready", we maintain two
"delay queues" in the kernel (each of 4k). In a first step, both queues
are filled, and the values are read from the first queue, if this queue
is finished, we read values from the second queue and fill the first
queue with new values from the trace file etc. Therefore we have a user
space process running, which reads the values from the trace file, and
sends them to the kernel.
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