#pragma section-numbers on
#pragma keywords Linux, Kernel, Operative System, Linus Torvalds, Open Source, drivers
#pragma description Summary of the changes and new features merged in the Linux Kernel during the 2.6.39 development cycle


/!\ The changelog is not ready due to lazyness^Wtime constraints. /!\ It will be completed in the next days and, of course, it will be ready again for 2.6.40. Meanwhile, you can check the kernel reports in LWN [https://lwn.net/Articles/433854/ (1], [https://lwn.net/Articles/434637/ 2], [https://lwn.net/Articles/435716/ 3)] or H Open [http://www.h-online.com/open/features/What-s-new-in-Linux-2-6-39-1242910.html (1)]


[[TableOfContents()]]
= Prominent features (the cool stuff) =

== Ext4 SMP scalability ==
In 2.6.37, huge Ext4 scalability improvements were merged and [http://kernelnewbies.org/Linux_2_6_37#head-5b9d7940fa4e8294ceaac86a74beb021b2fce3e3 mentioned in the changelog]. But this feature was not ready for prime time and had been disabled in source before the release - something that the changelog didn't mention. In this release it has been enabled by default. This is the text from the previous changelog:

"In this release Ext4 will use the "bio" layer directly instead of the intermediate "buffer" layer. The "bio" layer (alias for Block I/O: it's the part of the kernel that sends the requests to the IO/O scheduler) was one of the first features merged in the Linux 2.5.1 kernel. The buffer layer has a lot of performance and SMP scalability issues that will get solved with this port. A FFSB benchmark in a 48 core AMD box using a 24 SAS-disk hardware RAID array with 192 simultaneous ffsb threads speeds up by 300% (400% disabling journaling), while reducing CPU usage by a factor of 3-4"

Code: [http://git.kernel.org/linus/6fd7a46781999c32f423025767e43b349b967d57 (commit)]


== IPset ==

Official IPset webpage: [http://ipset.netfilter.org/ http://ipset.netfilter.org/]

IPset allows the creation of groups of network resources (IPv4/v6 addresses, TCP/UDP port numbers, IP-MAC address pairs, IP-port number pairs, etc), called "IP sets", then you can use those sets to define Netfilter/iptables rules. These sets are much more lookup-efficient than bare iptables rules, but may come with a greater memory footprint. Different storage algorithms (for the data structures in memory) are provided in ipset for the user to select an optimum solution. IPset has been available for some time in the xtables-addons patches and is now being included in the Linux tree.

This tool is useful to do things like: store multiple IP addresses or port numbers and match against the collection by iptables at one swoop; dynamically update iptables rules against IP addresses or ports without performance penalty; express complex IP address and ports based rulesets with one single iptables rule and benefit from the speed of IP sets.

Code: [http://git.kernel.org/linus/a7b4f989a629493bb4ec4a354def784d440b32c4 (commit 1], [http://git.kernel.org/linus/72205fc68bd13109576aa6c4c12c740962d28a6c 2], [http://git.kernel.org/linus/de76021a1bb35e3560afccf741d1119a872aea49 3], [http://git.kernel.org/linus/6c027889696a7a694b0e2f6e3cabadefec7553b6 4], [http://git.kernel.org/linus/543261907dc3c4e90845acfcd602ebdbfdfcb4f0 5], [http://git.kernel.org/linus/07896ed37b94599a1b8ea97f4bd5766be71390f4 6], [http://git.kernel.org/linus/5663bc30e6114b6ba88cc428619ede46a3246a7b 7], [http://git.kernel.org/linus/41d22f7b2e48c77175b62cec3797d7d7173a626e 8], [http://git.kernel.org/linus/b38370299eeaba4cf8a9e0c5c6acc2a1e049be23 9], [http://git.kernel.org/linus/21f45020a3084f80fcdd5f056a0c6389f5406399 10)]

== Btrfs updates ==
Btrfs allows different compression and copy-on-write settings for each file/directory (in addition to the per-filesystem controls). There is also the usual round of minor speedups, and tracepoints for runtime analysis.

Code: [http://git.kernel.org/linus/75e7cb7fe0c391561bd3af36515be3f3c64a04c6 (commit 1], [http://git.kernel.org/linus/32471f6e1983922473573da62cbee58699574aa4 2], [http://git.kernel.org/linus/c622ae6085d0c6ad834213bbf1477eb311359078 3], [http://git.kernel.org/linus/240f62c8756df285da11469259b3900f32883168 4], [http://git.kernel.org/linus/1abe9b8a138c9988ba8f7bfded6453649a31541f 5)]


== Transcendent Memory ==
Recommended LWN article: [https://lwn.net/Articles/340080/ Transcendent memory]

Trascendent memory is a new type of memory with a particular set of characteristics. From LWN: "transcendental memory can be thought of as a sort of RAM disk with some interesting characteristics: nobody knows how big it is, writes to the disk may not succeed, and, potentially, data written to the disk may vanish before being read back again". This memory could be used in places like the page cache, swap, or virtualization. In this release it is used for to implement a compressed in-memory caching mechanism called zcache.

Code: [http://git.kernel.org/linus/daa6afa6d920a389015bb8f1ea519cef0636f528 (commit 1], [http://git.kernel.org/linus/9cc06bf88d554dd527ded26eab28eec6a0d0e3df 2], [http://git.kernel.org/linus/6630889735ec3d950b4f1496ada77df287d8ee1b 3)]

== BKL: That's all, folks  ==
In 2.6.37, it was possible to compile a Linux kernel without support for the BKL. In this release, the BKL has been removed completely from the kernel sources, including the functions lock_kernel() and unlock_kernel().

Code: [http://git.kernel.org/linus/4ba8216cd90560bc402f52076f64d8546e8aefcb (commit)]

== Open-by-handle syscalls ==

Recommended LWN article: [https://lwn.net/Articles/375888/ Open by handle]

Two new syscalls have been added, name_to_handle_at() and open_by_handle_at(). These syscalls return a file handle, which is useful for user-space filesystems, backup software and other storage management tools. These handles can be used in a new flag that has been added to the open() syscall: O_PATH.


Code [http://git.kernel.org/linus/990d6c2d7aee921e3bce22b2d6a750fd552262be (commit)], [http://git.kernel.org/linus/becfd1f37544798cbdfd788f32c827160fab98c1 (commit)], [http://git.kernel.org/linus/7dadb755b082c259f7dd4a95a3a6eb21646a28d5 (commit)], [http://git.kernel.org/linus/6aae5f2b2085c5c90964bb78676ea8a6a336e037 (commit)], [http://git.kernel.org/linus/1abf0c718f15a56a0a435588d1b104c7a37dc9bd (commit)], [http://git.kernel.org/linus/bcda76524cd1fa32af748536f27f674a13e56700 (commit)]


= Drivers and architectures =
All the driver and architecture-specific changes can be found in the [http://kernelnewbies.org/Linux_2_6_38-DriversArch Linux_2_6_39-DriversArch page]

= Core =
= CPU scheduler =
= Memory management =
= Block =
= File systems =
''9p''
 * Add buffered write support for v9fs. [http://git.kernel.org/linus/7263cebed9fadad719063fdc8bba7085cf2c080d (commit)]
 * Add direct IO support in cached mode [http://git.kernel.org/linus/e959b54901e835f062ac8d44107bc543b66f0364 (commit)]
 * Add posixacl mount option [http://git.kernel.org/linus/e782ef71097e832f62256370a2fe231b9fba96cf (commit)]
''GFS2''
 * Deallocation performance patch [http://git.kernel.org/linus/4c16c36ad62fff8485215bd803d778eb2bd0b8bd (commit)]
 * Improve cluster mmap scalability [http://git.kernel.org/linus/b9c93bb7deadc7cdd00415edc6b38d67a26c1c7a (commit)]
 * Introduce AIL lock [http://git.kernel.org/linus/d6a079e82efd5fcbb1c7295f22e123c2cc748018 (commit)]
 * Use RCU for glock hash table [http://git.kernel.org/linus/bc015cb84129eb1451913cfebece270bf7a39e0f (commit)]

''HPFS''
 * Make HPFS compile on preempt and SMP [http://git.kernel.org/linus/637b424bf8747e50bab6648ab919632d6efd6c28 (commit)]
 * Implement fsync for hpfs [http://git.kernel.org/linus/bc8728ee56bca62df269b2dd159bc60838ac8e80 (commit)]
 * Remove CR/LF conversion option [http://git.kernel.org/linus/0fe105aa29bed0994991462b58ef61646db0e459 (commit)]



= Crypto =
= Virtualization =
= Security =
= Tracing/perf =

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CategoryReleases