Miscellaneous changes in 2.6.x.

Greatly improved multithreading support (2.6.0).
- Allows modern NPTL threading implementation to achieve better performance and much closer POSIX compliance than LinuxThreads.
- New arguments and additional flags for clone(2).
- New system calls: exit_group(2), tgkill(2), get_thread_area(2), set_thread_area(2), set_tid_address(2).
- New futex(2) system call supports faster implementation of mutexes and semaphores.

semtimedop(2) == semop() with timeout, for System V semaphores (2.6.0)
- For applications that make heavy use of semaphore operations with timeouts (some database management systems).
- Subsequently backported into 2.4.22.
- Not specified in SUSv3; available on Solaris 9 and HP-UX 11.

Hard CPU affinity: sched_setaffinity(2) (2.6.0).
- Used on multiprocessor system to confine process to subset of the CPUs.
- Can be used to maximize throughput and response of a single process, by placing all other processes on another CPU.
- Can prevent performance cost of cache invalidation that occurs if process times out on one CPU and is rescheduled on another.
- Even without sched_setaffinity(2), Linux kernel attempts to provide soft CPU affinity to reduce performance chances of cache invalidation.

/proc/sys/kernel/core_pattern specifies a template used to name all core dump files (2.6.0).

Core file name can include: name of executable file, time of dump (seconds since Epoch), PID, real UID/GID of process, number of terminating signal, name of host system (sethostname(2)).
See proc(5) manual page.