BUFSIZ = 1024, still ?

[Matthew Jacob]

On 8/18/2012 2:05 PM, Poul-Henning Kamp wrote:
> In message <5030033B.4060705 at feral.com>, Matthew Jacob writes:
>> On 8/18/2012 1:32 PM, Poul-Henning Kamp wrote:
>>> Shouldn't we at least increase it to pagesize ?
>>>
>> What data suggests to you it would be better at pagesize?
> The number of system calls to fwrite() a big file ?
>
> What evidence would there be that it would hurt ?
>
I am normally not this conservative, but I see this as "why make a 
change"? If you're concerned about performance, you won't be using 
fwrite, you'll use O_DIRECT and do your own alignment. But I see your point.

One could vaguely argue that a 4K BUFSIZ will put at risk more data on 
crashes needlessly. One could also vaguely say that the write syscall 
isn't expensive in and of itself, and that there might be a measurable 
difference for having to copy 4K (unaligned) than 1K (unaligned) to 
kernel space for disposition.

Wasn't there just a recent discussion about running 1.x binaries? One 
reason we can do things like that is basic constants don't change very 
often. I believe the last time I saw BUFSIZ change was from BSD 2.9 to 
BSD 4.0, but I probably misremember that.

If you're going to talk about making a change to defaults, the default 
MAXPHYS and DLFTPHYS have been undersized for years now.