Re: [PATCH] Avoid accessing a slow working copy during diffcore operations.

On 12/14/06, Johannes Schindelin <Johannes.Schindelin@gmx.de> wrote:
> > > If Git is compiled with NO_FAST_WORKING_DIRECTORY set then we will
> > > avoid looking at the working directory when the blob in question
> > > is available within a packfile and the caller doesn't need the data
> > > unpacked into a temporary file.
> >
> > Why can't it be useful in generic code? What are the downsides?
>
> It is usually cheaper to just read the file, especially if it is still
> cached, because the alternative means unpacking the loose object, or
> worse, unpacking the packed object _along_ with the objects in its delta
> chain.

But you have to read less, and even that could be in cache as well
and unpacking in userspace could be faster than open/write temporary/
read temporary/close/unlink temporary file on a normal system

> Not every OS sucks cache-wise, and you should not make others suffer for
> Redmond's shortcomings.

I'm just do not understand why avoiding temporary file wouldn't help
all OSes, even if they do not suck cache-wise.
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