Andrew Morton <[email protected]> writes:
> On Tue, 11 Sep 2007 14:12:26 +0200 Jörn Engel <[email protected]> wrote:
>
>> While I agree with your concern, those numbers are quite silly. The
>> chances of 99.8% of pages being free and the remaining 0.2% being
>> perfectly spread across all 2MB large_pages are lower than those of SHA1
>> creating a collision.
>
> Actually it'd be pretty easy to craft an application which allocates seven
> pages for pagecache, then one for <something>, then seven for pagecache, then
> one for <something>, etc.
>
> I've had test apps which do that sort of thing accidentally. The result
> wasn't pretty.
Except that the applications 7 pages are movable and the <something>
would have to be unmovable. And then they should not share the same
memory region. At least they should never be allowed to interleave in
such a pattern on a larger scale.
The only way a fragmentation catastroph can be (proovable) avoided is
by having so few unmovable objects that size + max waste << ram
size. The smaller the better. Allowing movable and unmovable objects
to mix means that max waste goes way up. In your example waste would
be 7*size. With 2MB uper order limit it would be 511*size.
I keep coming back to the fact that movable objects should be moved
out of the way for unmovable ones. Anything else just allows
fragmentation to build up.
MfG
Goswin
-
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/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
