From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: Jiri Slaby <jslaby@suse.com>,
Pengutronix Kernel Team <kernel@pengutronix.de>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v1 0/3] reduce tty latency
Date: Thu, 10 Jan 2019 14:51:53 +0100 [thread overview]
Message-ID: <20190110135153.GA9966@kroah.com> (raw)
In-Reply-To: <20190110101232.9398-1-o.rempel@pengutronix.de>
On Thu, Jan 10, 2019 at 11:12:29AM +0100, Oleksij Rempel wrote:
> This patch set is reducing latency on tty path.
> For testing I used hackbench running on all cores of 4 core system and
> high prioritized application sending and receiving packets over tty interface
> with loop-back adapter.
Odd, all of these ended up in my spam folder, you might want to check
your server email settings...
> Results without this patches:
> latency histogram:
> 0 ... < 250 usec : 1933104 transmissions
> 250 ... < 500 usec : 21339 transmissions
> 500 ... < 750 usec : 8952 transmissions
> 750 ... < 1000 usec : 6226 transmissions
> 1000 ... < 1500 usec : 7688 transmissions
> 1500 ... < 2000 usec : 5236 transmissions
> 2000 ... < 5000 usec : 11724 transmissions
> 5000 ... < 10000 usec : 3588 transmissions
> 10000 ... < 50000 usec : 2123 transmissions
> 50000 ... < 1000000 usec : 20 transmissions
> >= 1000000 usec : 0 transmissions
>
> Test results after this patches:
> min latency: 0 sec : 75 usec
> max latency: 0 sec : 125 usec
> average latency: 81 usec
> latency measure cycles overall: 79000000
> latency histogram:
> 0 ... < 250 usec : 79000000 transmissions
> 250 ... < 500 usec : 0 transmissions
> 500 ... < 750 usec : 0 transmissions
> 750 ... < 1000 usec : 0 transmissions
> 1000 ... < 1500 usec : 0 transmissions
> 1500 ... < 2000 usec : 0 transmissions
> 2000 ... < 5000 usec : 0 transmissions
> 5000 ... < 10000 usec : 0 transmissions
> 10000 ... < 50000 usec : 0 transmissions
> 50000 ... < 1000000 usec : 0 transmissions
> >= 1000000 usec : 0 transmissions
> average no. of read calls to assemble the packet: 1
Like Linus said, who runs a real-world system that cares about this
latency measurement?
Yes, it might be fun for odd benchmarks to show the value of one RT
patchset/OS vs. another one, but this change can cause real issues in
real systems that do real, non-serial-loopback work.
thanks,
greg k-h
prev parent reply other threads:[~2019-01-10 13:51 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-01-10 10:12 [PATCH v1 0/3] reduce tty latency Oleksij Rempel
2019-01-10 10:12 ` [PATCH v1 1/3] drivers/tty: refactor functions for flushing/queuing work Oleksij Rempel
2019-03-11 8:16 ` Alexander Sverdlin
2019-01-10 10:12 ` [PATCH v1 2/3] drivers/tty: convert tty_port to use kthread_worker Oleksij Rempel
2019-03-11 8:23 ` Alexander Sverdlin
2019-01-10 10:12 ` [PATCH v1 3/3] drivers/tty: increase priority for tty_buffer_worker Oleksij Rempel
2019-01-10 12:54 ` Linus Torvalds
2019-01-10 15:19 ` Oleksij Rempel
2019-01-10 16:30 ` Greg Kroah-Hartman
2019-01-28 8:05 ` Oleksij Rempel
2019-01-28 8:23 ` Greg Kroah-Hartman
2019-01-28 9:22 ` Oleksij Rempel
2019-01-28 20:03 ` Linus Torvalds
2019-01-28 20:13 ` Linus Torvalds
2019-01-10 16:59 ` Linus Torvalds
2019-03-11 8:24 ` Alexander Sverdlin
2019-01-10 13:51 ` Greg Kroah-Hartman [this message]
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