2.6.9

Released October 19, 2004 [http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.9 changelog]
Token-based thrashing control [http://lwn.net/Articles/96621 (LWN article)] [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=e6a32818710d24cc910ec4d4333f99972b3cf563 (commit)]
Concurrent O_SYNC write support: In databases it is common to have multiple threads or processes performing O_SYNC writes against different parts of the same file.[http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=96deebee4470587bc1a855c787d6919df681cdac (commit)]
Reiserfs v3 barrier support: Add reiserfs support for flush barriers, mount with -o barrier=flush to enable them. Barriers are triggered on fsync and for log commits [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=b736095823b073209ef38622227c64c593260b73 (commit)]
ext3 barrier support: Mount with "mount -o barrier=1" to enable barriers [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=52a75614f1f753e01a5a9610c5390b5b7f795912 (commit)]
Support of disk barriers: [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=74c50b2c1af1b3535cf6c39ce684e60fa9f5dfdb (commit)]
m32r architecture support
Scheduler statistics: adds lots of CPU scheduler stats in /proc/$PID/stat [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=34b334118622daae225ab8fd56c79f54f6e15774 (commit)]
RLIMIT_MEMLOCK semantics change: In Linux kernels before 2.6.9, only privileged processes (CAP_IPC_LOCK) could lock memory, and the RLIMIT_MEMLOCK soft resource limit placed an upper limit on the number of bytes that a privileged process can lock. Since kernel 2.6.9: no limits are placed on the amount of memory that a privileged process can lock; and an unprivileged process is now able to lock memory up to the soft limit defined by RLIMIT_MEMLOC [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=adaeb8014406050050cf09416d1b0e3c23838fdb (commit)]
Tunable "max sectors" limit for block I/O requests (can help latency reduction)
New prctl() option allowing programs to change their name (PR_GET_NAME)
AMD dual-core support
Out-of-line spinlocks [http://lwn.net/Articles/97537/ (LWN article)] [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=2ea380e357f23ad37c1a06c6af509b68e9d57bb6 (commit)]
Support for POSIX's waitid() Also, now linux now supports the POSIX specification that SIGCHLD is sent to the parent when one of its children resumes as a consequence of receiving a SIGCONT signal. Also, WCONTINUED flag is added to waitpid() and waitid() [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=8e81583bfd488bb0b10aa799f7ec5f7b4a79fe73 (commit)].
Shared memory scalability improvements
"flex mmap" user-space memory layout [http://lwn.net/Articles/91829/ (LWN article)] [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=0f7c9b1849d5365d27d4553e471a8e721c8dabb7 (commit)]
x86 PAE swapspace expansion. PAE is artificially limited in terms of swapspace to the same bitsplit as ordinary i386, a 5/24 split (32 swapfiles, 64GB max swapfile size), when a 5/27 split (32 swapfiles, 512GB max swapfile size) is feasible. This patch transparently removes that limitation by using more of the space available in PAE's wider ptes for swap ptes [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=7c1c60d14d175c41c5db03f20f44c80c4d683e52 (commit)]
Show Active/Inactive on per-node meminfo: The patch below enable to display the size of Active/Inactive pages on per-node meminfo (/sys/devices/system/node/node%d/meminfo) like /proc/meminfo [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=6d4a504b45abc756eac6374591f74c7afb722b6a (commit)]
Change in TCP ICMP source quench behavior
[http://www.linux-usb.org/gadget/h2-otg.html USB "on the go" support]
New USB storage driver
Support for more than eight partitions on BSD-labeled disks
Ethtool support in the loopback driver
NETIF_F_LLTX interface [http://lwn.net/Articles/101215/ (LWN article)]
DSCP decapsulation for IPsec [http://kernel.org/git/?p=linux/kernel/git/torvalds/old-2.6-bkcvs.git;a=commit;h=cac8c9f3e6cd37a3dd079e12a01fc41d2650bf39 (commit)]
Removal of the ancient "busmouse" driver
Infrastructure for cluster-wide file locking
DRM subsystem cleanups
"fake NUMA" mode for x86-64 testing
Small-footprint tmpfs implementation
Support for scheduler profiling (seeing where context switches come from)
Automatic TCP window scaling calculation
Some VFS interface improvements
Executable support in hugetlb mappings
The Whirlpool digest algorithm
Removal of the very last suser() call