linux-kernel - Re: [PATCH v3 2/2] TTY: tty flip buffer optimisation.

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Message-ID: <20111114150523.2abdf7a1@lxorguk.ukuu.org.uk>
Date:	Mon, 14 Nov 2011 15:05:23 +0000
From:	Alan Cox <alan@...rguk.ukuu.org.uk>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	Ilya Zykov <ilya@...x.ru>, Alan Cox <alan@...ux.intel.com>,
	linux-kernel@...r.kernel.org, Greg Kroah-Hartman <gregkh@...e.de>,
	Jiri Slaby <jirislaby@...il.com>
Subject: Re: [PATCH v3 2/2] TTY: tty flip buffer optimisation.

> Hi, the results are indeed nice. However is there any *real* load other
> than this tailor-made microbenchmark where the added code complexity is
> worth it?

I'm wondering if we need the complexity in the first place. Certainly 256
does seem a bit small for pty/tty traffic. A 'real world' benchmark would
be an ls -lR / on a machine with a fast graphics card or in console mode

ie

ls -lR /		# prime cache
time ls -lR /

and there are cases where people do a lot of traffic over a pty like this
so I don't think it's entirely fake.

I don't like the complexity but we could certainly go from using 256 byte
buffers to "tty->buf.bufsize" and make it configurable without
that complexity.

Alan
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