2.6.9

• Released October 19, 2004 changelog

• Token-based thrashing control (LWN article) (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.(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 (commit)

• ext3 barrier support: Mount with "mount -o barrier=1" to enable barriers (commit)

• Support of disk barriers: (commit)

• m32r architecture support

• Scheduler statistics: adds lots of CPU scheduler stats in /proc/$PID/stat (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 (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 (LWN article) (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() (commit).

• Shared memory scalability improvements

• "flex mmap" user-space memory layout (LWN article) (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 (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 (commit)

• Change in TCP ICMP source quench behavior

• 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 (LWN article)

• DSCP decapsulation for IPsec (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