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

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Date:   Tue, 9 Jan 2018 02:35:45 +0000
From:   Chris Mi <chrism@...lanox.com>
To:     Phil Sutter <phil@....cc>
CC:     "dsahern@...il.com" <dsahern@...il.com>,
        "marcelo.leitner@...il.com" <marcelo.leitner@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "gerlitz.or@...il.com" <gerlitz.or@...il.com>,
        "stephen@...workplumber.org" <stephen@...workplumber.org>
Subject: RE: [patch iproute2 v6 0/3] tc: Add -bs option to batch mode

> -----Original Message-----
> From: n0-1@...yte.nwl.cc [mailto:n0-1@...yte.nwl.cc] On Behalf Of Phil
> Sutter
> Sent: Monday, January 8, 2018 9:32 PM
> To: Chris Mi <chrism@...lanox.com>
> Cc: dsahern@...il.com; marcelo.leitner@...il.com;
> netdev@...r.kernel.org; gerlitz.or@...il.com;
> stephen@...workplumber.org
> Subject: Re: [patch iproute2 v6 0/3] tc: Add -bs option to batch mode
> 
> Hi Chris,
> 
> On Mon, Jan 08, 2018 at 02:03:53AM +0000, Chris Mi wrote:
> > > On Thu, Jan 04, 2018 at 04:34:51PM +0900, Chris Mi wrote:
> > > > The insertion rate is improved more than 10%.
> > >
> > > Did you measure the effect of increasing batch sizes?
> > Yes. Even if we enlarge the batch size bigger than 10, there is no big
> improvement.
> > I think that's because current kernel doesn't process the requests in
> parallel.
> > If kernel processes the requests in parallel, I believe specifying a
> > bigger batch size will get a better result.
> 
> But throughput doesn't regress at some point, right? I think that's the critical
> aspect when considering an "unlimited" batch size.
> 
> On Mon, Jan 08, 2018 at 08:00:00AM +0000, Chris Mi wrote:
> > After testing, I find that the message passed to kernel should not be too
> big.
> > If it is bigger than about 64K, sendmsg returns -1, errno is 90 (EMSGSIZE).
> > That is about 400 commands.  So how about set batch size to 128 which is
> big enough?
> 
> If that's the easiest way, why not. At first, I thought one could maybe send
> the collected messages in chunks of suitable size, but that's probably not
> worth the effort.
I did a testing. If we read a million commands in memory and send them in chunks of 128,
we'll have a big regression. It takes about 21 seconds.