Messages in this thread | | | From | "Rafael J. Wysocki" <> | Subject | Re: [RFC] [PATCH 0/5] Dynamically allocated pageflags. | Date | Tue, 24 Jul 2007 00:05:21 +0200 |
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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
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