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==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: "[http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.3.2392 Transparent Operating System Support for Superpages]".

===Linux===

* They were a [http://lwn.net/Articles/40840/ 2003 Kernel Summit] topic

* 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>get_large_pages(2)</tt> and <tt>shared_large_pages(2)</tt>, as covered in [http://lwn.net/Articles/6969/ this LWN article] ~~(along with <tt>free_hugepages</tt>,~~ present in kernels 2.5.36-2.5.54~~) was~~ a first attempt to provide explicit large page support to applications.

* <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://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.

===Applications===

* [[MySQL]] can use hugetlbfs via the <tt>large-pages</tt> option

* [[kvm]] can use hugetlbfs with the <tt>--mem-path</tt> option since [http://www.linux-kvm.com/content/get-performance-boost-backing-your-kvm-guest-hugetlbfs kvm-62], released in late 2008

===Page Clustering===

==Page Clustering==

Page clustering (implemented by [http://lwn.net/Articles/23785/ William Lee Irwin] for Linux in 2003, and not to be confused with page-granularity [http://lwn.net/Articles/297299/ swap-out clustering]). There's good coverage in this [http://kerneltrap.org/node/620 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, "[http://ols.fedoraproject.org/OLS/Reprints.../Reprint-Irwin-OLS2003.pdf A 2.5 Page Clustering Implementation]".

Pages: Difference between revisions

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 ==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: "[http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.3.2392 Transparent Operating System Support for Superpages]".
 ===Linux===
-* They were a [http://lwn.net/Articles/40840/ 2003 Kernel Summit] topic
+* 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>get_large_pages(2)</tt> and <tt>shared_large_pages(2)</tt>, as covered in [http://lwn.net/Articles/6969/ this LWN article] (along with <tt>free_hugepages</tt>, present in kernels 2.5.36-2.5.54) was a first attempt to provide explicit large page support to applications.
+* <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://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.
+===Applications===
+* [[MySQL]] can use hugetlbfs via the <tt>large-pages</tt> option
 * [[kvm]] can use hugetlbfs with the <tt>--mem-path</tt> option since [http://www.linux-kvm.com/content/get-performance-boost-backing-your-kvm-guest-hugetlbfs kvm-62], released in late 2008
-===Page Clustering===
+==Page Clustering==
 Page clustering (implemented by [http://lwn.net/Articles/23785/ William Lee Irwin] for Linux in 2003, and not to be confused with page-granularity [http://lwn.net/Articles/297299/ swap-out clustering]). There's good coverage in this [http://kerneltrap.org/node/620 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, "[http://ols.fedoraproject.org/OLS/Reprints.../Reprint-Irwin-OLS2003.pdf A 2.5 Page Clustering Implementation]".