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===Linux===
===Linux===
* They were a [http://lwn.net/Articles/40840/ 2003 Kernel Summit] topic, after seeing first [http://kerneltrap.org/node/418 introduction] in Linux 2.5.36 ([http://linuxgazette.net/155/krishnakumar.html LinuxGazette] primer article)
* They were a [http://lwn.net/Articles/40840/ 2003 Kernel Summit] topic, after seeing first [http://kerneltrap.org/node/418 introduction] in Linux 2.5.36 ([http://linuxgazette.net/155/krishnakumar.html LinuxGazette] primer article)
* <tt>alloc_hugepages</tt>, <tt>free_hugepages</tt>, <tt>get_large_pages(2)</tt> and <tt>shared_large_pages(2)</tt>, as covered in [http://lwn.net/Articles/6969/ this LWN article] and present in kernels 2.5.36-2.5.54, were a first attempt to provide explicit large page support to applications.
* [http://lwn.net/Articles/6971/ Rohit Seth] provided the first explicit large page support to applications as covered in [http://lwn.net/Articles/6969/ this LWN article]
** <tt>alloc_hugepages</tt>, <tt>free_hugepages</tt>, <tt>get_large_pages(2)</tt> and <tt>shared_large_pages(2)</tt>, present in kernels 2.5.36-2.5.54
* [http://www.mjmwired.net/kernel/Documentation/vm/hugetlbpage.txt hugetlbfs] and assorted infrastructure replaced these. Mel Gorman's [http://linux-mm.org/HugePages Linux MM wiki] has a good page on hugetlbfs.
* [http://www.mjmwired.net/kernel/Documentation/vm/hugetlbpage.txt hugetlbfs] and assorted infrastructure replaced these. Mel Gorman's [http://linux-mm.org/HugePages Linux MM wiki] has a good page on hugetlbfs.



Revision as of 05:39, 19 June 2009

Huge Pages

Making pages larger means fewer TLB misses for a given TLB size (due to more pages being supportable in the same amount of memory, due to narrower page identifiers), large mapping/releasing operations will be faster (due to fewer page table entries needing to be handled), and less memory is devoted to page table entries for a given amount of memory being indexed. The downside is possible wastage of main memory (due to pages not being used as completely). A 2002 paper from Navarro et al at Rice proposed transparent operating system support: "Transparent Operating System Support for Superpages".

Linux

Applications

  • MySQL can use hugetlbfs via the large-pages option
  • kvm can use hugetlbfs with the --mem-path option since kvm-62, released in late 2008

Page Clustering

Page clustering (implemented by William Lee Irwin for Linux in 2003, and not to be confused with page-granularity swap-out clustering). There's good coverage in this KernelTrap article. This is essentially huge pages without hardware support, and therefore with some overhead and no improvements in TLB-relative performance. It was written up in Irwin's 2003 OLS paper, "A 2.5 Page Clustering Implementation".