On Tue, May 08, 2007 at 07:57:37PM -0700, Christoph Lameter wrote: > On Wed, 9 May 2007, Nick Piggin wrote: > > > > Exactly. That overhead does not exist in SLUB. Thus SLOB is less efficient > > > than SLUB. > > > > What you trade for that is that one page page can only serve one slab. > > Right. > > > For small systems, I would not be surprised if that was less space > > efficient, even just looking at kmalloc caches in isolation. Or do you > > have numbers to support your conclusion? > > No I do not have any number beyond the efficiency calculations based on > whole slabs. We would have to do some experiments to figure out how much > space is actually wasted through partial slabs.
The expectation would be (PAGE_SIZE + (PAGE_SIZE % size))/2 on average per cache. > The situation becomes different with allocation and frees. Then we may > have lots of partial slabs that we allocate from. But the SLOB approach > also will have holes to manage. So I do not see how this could be a > benefit unless you only have a few precious pages and you need to put > multiple object sizes into it. A 4M system still has 1000 pages. A 4M system has approximately zero pages free once you've actually got stuff running in userspace. The marginal utility of each page is very high. -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
