Re: [PATCH] Limit the size of the new delta_base_cache

From: Linus Torvalds <torvalds@linux-foundation.org>
Date: Mar 19, 2007, 17:07 UTC
Message-ID: <Pine.LNX.4.64.0703191004560.6730@woody.linux-foundation.org>
In-Reply-To: <alpine.LFD.0.83.0703191218190.18328@xanadu.home>

On Mon, 19 Mar 2007, Nicolas Pitre wrote:

> 
> In fact, the bigger is the object, the more effective will be the cache.

Yes. BUT ONLY IF THE CACHE ISN'T SIZE-LIMITED!

Once you limit the size of the cache, you change the whole equation.

It's usually *more* expensive to re-parse two half-sized objects than it is to parse one large object. So if you have to choose between throwing out two small objects or throwing out one large one, you should choose the single large one.

Which totally throws your argument out of the window. It's simply not true any more: the cache will *not* be more effective the larger the objects are, because you are ignoring the fact that adding a large object will *remove* many small ones.

So if I were Junio, I wouldn't accept your patch as it is now. Your argument is simply fundamentally flawed.

		Linus