Re: [patch iproute2 v6 0/3] tc: Add -bs option to batch mode

Hi Chris,

On Thu, Jan 04, 2018 at 04:34:51PM +0900, Chris Mi wrote:

Currently in tc batch mode, only one command is read from the batch
file and sent to kernel to process. With this patchset, we can accumulate
several commands before sending to kernel. The batch size is specified
using option -bs or -batchsize.

To accumulate the commands in tc, client should allocate an array of
struct iovec. If batchsize is bigger than 1, only after the client
has accumulated enough commands, can the client call rtnl_talk_msg
to send the message that includes the iov array. One exception is
that there is no more command in the batch file.

But please note that kernel still processes the requests one by one.
To process the requests in parallel in kernel is another effort.
The time we're saving in this patchset is the user mode and kernel mode
context switch. So this patchset works on top of the current kernel.

Using the following script in kernel, we can generate 1,000,000 rules.
	tools/testing/selftests/tc-testing/tdc_batch.py

Without this patchset, 'tc -b $file' exection time is:

real    0m15.555s
user    0m7.211s
sys     0m8.284s

With this patchset, 'tc -b $file -bs 10' exection time is:

real    0m13.043s
user    0m6.479s
sys     0m6.504s

The insertion rate is improved more than 10%.

Did you measure the effect of increasing batch sizes?

I wonder whether specifying the batch size is necessary at all. Couldn't
batch mode just collect messages until either EOF or an incompatible
command is encountered which then triggers a commit to kernel? This
might simplify code quite a bit.

Cheers, Phil