From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: rwhite@pobox.com
Cc: Andries Brouwer <aebr@win.tue.nl>,
Russell King <rmk@arm.linux.org.uk>, Ed Vance <EdV@macrolink.com>,
"'Theodore Tso'" <tytso@mit.edu>,
linux-kernel@vger.kernel.org, linux-serial@vger.kernel.org
Subject: Re: n_tty.c driver patch (semantic and performance correction) (a ll recent versions)
Date: 28 Jul 2002 21:04:36 +0100 [thread overview]
Message-ID: <1027886676.790.5.camel@irongate.swansea.linux.org.uk> (raw)
In-Reply-To: <200207271934.27102.rwhite@pobox.com>
On Sun, 2002-07-28 at 03:34, Robert White wrote:
> Having virtually every user on the planet realize this and just set VMIN == 1
> is an fairly telling indicator.
>
> Repeatedly calling the kernel to assemble an input buffer which is necessary
> if VMIN ==1, is dumb.
VMIN was basically invented for communication protocols when you know
the block length that should arrive within a given timeout. Its pretty
much essential on old old boxes and was very important for
interrupt/context switch reduction when doing block transfers. In that
world the read blocks or in O_NDELAY returns -EAGAIN (0 in old SYS5)
until the data block is big enough to warrant its copying. Similarly
poll has no business saying data is ready until a large enough block is.
When talking to a human setting VMIN > 1 makes no sense anyway. In fact
nowdays it makes even less sense than it did before because of the use
of UTF8 encodings for unicode characters.
next prev parent reply other threads:[~2002-07-28 18:46 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-06-26 17:48 n_tty.c driver patch (semantic and performance correction) (a ll recent versions) Ed Vance
2002-06-26 20:42 ` Russell King
2002-06-27 16:37 ` Robert White
2002-07-26 14:17 ` Russell King
2002-07-27 22:07 ` Robert White
2002-07-27 23:11 ` Russell King
2002-07-27 23:21 ` Andries Brouwer
2002-07-28 2:34 ` Robert White
2002-07-28 3:01 ` Stevie O
2002-07-28 13:34 ` Andries Brouwer
2002-07-28 20:04 ` Alan Cox [this message]
2002-07-30 7:41 ` Robert White
2002-07-28 2:36 ` Robert White
-- strict thread matches above, loose matches on Subject: below --
2002-07-31 16:58 Ed Vance
2002-07-30 17:07 Ed Vance
2002-07-29 21:46 Ed Vance
2002-07-30 7:50 ` Robert White
2002-06-28 18:12 Ed Vance
2002-06-17 17:27 Ed Vance
2002-06-18 2:00 ` Robert White
2002-06-18 13:05 ` Stuart MacDonald
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