Re: [RFC \ WISH] Add -o option to git-rev-list

From: Linus Torvalds <torvalds@osdl.org>
Date: Dec 11, 2006, 00:51 UTC
Message-ID: <Pine.LNX.4.64.0612101647310.12500@woody.osdl.org>
In-Reply-To: <e5bfff550612101615u5f588513n499e3b88ce14a6f6@mail.gmail.com>

On Mon, 11 Dec 2006, Marco Costalba wrote:

> 
> But it's still slow. Almost one second (985ms) to read the little qgit repo:

Right. Because every time you sleep, you sleep for 100 ms.

That's why I was saying that you need to add polling to the thing. I don't know what the QT interfaces to asynchronous polling file descriptors are, but as long as you just blindly wait for 100ms whenever you run out of data, things will always suck.

Using "fread()" hid this problem, because the thing would block in fread(), and thus you'd nor see as many of these events.

> As a compare the temporary file version needs a mere 105ms (1030 revs).

How about you just compare something simpler:

	git-rev-list | cat > /dev/null

vs

	git-rev-list > tmpfile ; cat tmpfile > /dev/null

and see which one works better.

If the pipe works better, that means that it's your code that is buggy and broken.

Which gets us back to the basic issue: you're asking for a bad interface.

This is your problem:

> 		guiUpdateTimer.start(100, true);

rather than just blindly starting a timer, you should ask it to wait until more data is available.