From: H. Peter Anvin <hpa@zytor.com>
Date: Wed, 05 Oct 2005 02:48:51 GMT
Subject: Re: What to expect after 0.99.8
Message-ID: <43433F13.1080306@zytor.com>
In-Reply-To: <7vu0fx9c1c.fsf@assigned-by-dhcp.cox.net>

Junio C Hamano wrote:
> "H. Peter Anvin" <hpa@zytor.com> writes:
> 
>>If you have an ssh connection, you're writing over a pipe to the ssh 
>>process, and your local buffer is that pipe, which is PIPE_BUF size.
> 
> I vaguely recall there was an interesting regression in recent
> kernel history when the implementation of the pipe buffer was
> changed, with which, writing the same amount of data with
> different number of writes made things behave differently and
> making the worst case buffer size less than traditional 4K.
> 
> I wonder if we are going to be bitten by that one...
> 

The definition of PIPE_BUF is that a write to a pipe of no more than 
PIPE_BUF bytes will either succeed immediately or block; it will not be 
broken up into multiple writes (with potential interlace problems.)  It 
says *nothing* about what happens with multiple writes.

	-hpa