Hi,
On Monday, 23 July 2007 15:05, Nigel Cunningham wrote:
> Hi all.
>
> As we all know, pageflags have been a scarce resource for a while now. These
> patches seek to help address that issue by adding support for a new type
> of 'dynamically allocated' pageflag.
>
> The basic idea is that we use per node & zone bitmaps built out of order zero
> allocations, to replace bits in page->flags. Bitmaps can be sparse, being
> populated when a bit on the page is set, and returning zero for all bits in
> sparse pages. Untested hotplug support is included.
>
> This method of storing the data does of course come with a performance hit.
> I've included some simple timing loops in #ifdef'd code that help quantify
> that.
>
> Interestingly, the new implementation is actually quicker under some
> circumstances. In cases where the usage pattern involves operating on the
> flags for a number of pages in succession, the hit involved in getting the
> struct pages from main memory appears to be greater than that involved in
> calculating which unsigned long and bit to test.
>
> Tested only on UP (x86_64) so far.
How does it compare to the memory bitmaps used by swsusp, defined in
kernel/power/snapshot.c?
Greetings,
Rafael
--
"Premature optimization is the root of all evil." - Donald Knuth
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