lkml.org 
[lkml]   [2014]   [Feb]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] de-asmify the x86-64 system call slowpath

* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> [...]
>
> No, I was thinking "try to optimistically map 8 adjacent aligned
> pages at a time" - that would be the same cacheline in the page
> tables, so it would be fairly cheap if we couple it with a
> gang-lookup of the pages in the page cache (or, for anonymous pages,
> by just optimistically trying to do an order-3 page allocation, and
> if that works, just map the 32kB allocation you got as eight
> individual pages).
>
> I know it's been discussed at some point, and I even have a dim
> memory of having seen some really ugly patches.

I have a dim memory of having written such group-prefaulting patches
myself a decade ago or so - IIRC the main problem was that at that
time we never found a common load where it really mattered, and it was
easy to spend more time doing all this extra work and not see the
prefaulted pages used.

But the cost/benefit balance has indeed changed so IMO it's worth a
try.

Thanks,

Ingo


\
 
 \ /
  Last update: 2014-02-06 07:41    [W:1.142 / U:0.016 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site