Messages in this thread |  | | Date | Fri, 21 Feb 2014 10:13:54 -0800 | Subject | Re: [PATCH] mm: per-thread vma caching | From | Linus Torvalds <> |
| |
On Thu, Feb 20, 2014 at 9:28 PM, Davidlohr Bueso <davidlohr@hp.com> wrote: > From: Davidlohr Bueso <davidlohr@hp.com> > > This patch is a continuation of efforts trying to optimize find_vma(), > avoiding potentially expensive rbtree walks to locate a vma upon faults.
Ok, so I like this one much better than the previous version.
However, I do wonder if the per-mm vmacache is actually worth it. Couldn't the per-thread one replace it entirely?
Also, the hash you use for the vmacache index is *particularly* odd.
int idx = (addr >> 10) & 3;
you're using the top two bits of the address *within* the page. There's a lot of places that round addresses down to pages, and in general it just looks really odd to use an offset within a page as an index, since in some patterns (linear accesses, whatever), the page faults will always be to the beginning of the page, so index 0 ends up being special.
What am I missing?
Linus
|  |