2.6.39 merge window, part 2

• The ipset mechanism has been merged. Ipset allows the creation of groups of IP addresses, port numbers, and MAC addresses in a way which can be quickly matched in iptables rules.

• The size of the initial congestion window in the TCP stack has been increased, a change which should lead to shorter latencies for the loading of web pages and other server-oriented tasks. See this article for details.

• There is a new system call:

      int syncfs(int fd);
  

  It behaves like sync() with the exception that only the filesystem containing fd will be flushed to persistent storage.

• The USB core has gained support for USB 3.0 hubs.

• The transcendent memory core has been added to the staging tree. Along with it came "zcache," a compressed in-memory caching mechanism.

• There is a new "multi-queue priority scheduler" queueing discipline in the networking layer which enables the offloading of quality-of-service processing work to suitably capable hardware.

• The CHOKe flow scheduler and the Stochastic Fair Blue scheduler have been added to the networking code.

• RFC 4303 extended IPSEC sequence numbers are now supported.

• Support for the UniCore 32-bit RISC architecture has been merged.

• New drivers include:
  • Processors and systems: VIA/WonderMedia VT8500/WM85xx System-on-Chips, IMX27 IPCAM boards, and MX51 Genesi Efika Smartbook systems.

    Block: Broadcom NetXtreme II FCoE controllers and Freescale MXS Multimedia Card interfaces.

  • Graphics: Intel GMA500 controllers (2D acceleration only), USB-connected graphics devices, MXS LCD framebuffer devices, and LD9040 AMOLED panels.

  • Input: Hyper-V virtualized mice, Roccat Kova[+] mouse devices, Roccat Arvo keyboards, Wolfson WM831x PMIC touchscreen controllers, Atmel AT42QT1070 touch sensor chips, and Texas Instruments TSC2005 touchscreen controllers.

  • Networking: Texas Instruments WiLink7 bluetooth controllers (graduated from staging), Bosch C_CAN controllers, Faraday FTMAC100 10/100 Ethernet controllers, and the Xen "netback" back-end driver.

  • Miscellaneous: Faraday FUSB300 USB peripheral controllers, OMAP USBHS host controllers, NVIDIA Tegra USB host controllers, Texas Instruments PRUSS-connected devices, MSM UARTs, Maxim MAX517/518/519 DACs, RealTek PCI-E card readers, Analog Devices ad7606, ad7606-6, and ad7606-4 analog to digital converters, Maxim MAX6639 temperature monitors, Maxim MAX8688, MAX16064, MAX34440 and MAX34441 hardware monitoring chips, Lineage compact power line power entry modules, PMBus-compliant hardware monitoring devices, Linear Technology LTC4151 is high voltage I2C current and voltage monitors, Intel SCU watchdog devices, Ingenic jz4740 SoC hardware watchdogs, Xen watchdog devices, NVIDIA Tegra internal I2C controllers, Freescale i.MX28 I2C interfaces, MXS Application UART (AUART) ports, SuperH SPI controllers, Altera SPI controllers, OpenCores tiny SPI controllers, SMSC SCH5627 Super-I/O hardware monitoring chips, Texas Instruments ADS1015 12-bit 4-input ADC devices, Diolan U2C-12 USB adapters, SPEAr13XX PCIe controllers (in "gadget" mode), and Freescale MXS-based SoC i.MX23/28 DMA engines.

  • Sound: Firewire-connected sound devices, Wolfson Micro WM8991 codecs, Cirrus CS4271 codecs, Freescale SGTL5000 codecs, TI tlv320aic32x4 codecs, Maxim MAX9850 codecs, and TerraTec 6fire DMX USB interfaces.

  • Outgoing: A number of TTY drivers (epca, ip2, istallion, riscom8, serial167, specialix, stallion, generic_serial, rio, ser_a2232, sx, and vme_scc) have been moved to the staging tree in anticipation of removal in 2.6.41. The smbfs and autofs3 filesystems, which were moved to staging in 2.6.37, have now been moved out of the kernel entirely.

Changes visible to kernel developers include:

• After many years of work by a large number of developers, the big kernel lock has been removed from the kernel.

• The dynamic debug mechanism has some new control flags allowing for control over whether the function name, line number, module name, and current thread ID are printed.

• The kernel can export raw DMI table data via sysfs, making it available in user space without needing to go through /dev/mem.

• Network drivers can now enable hardware support for receive flow steering via the new ndo_rx_flow_steer() method.

• The "pstore" filesystem provides access to platform-specific persistent storage which can be used to carry information across reboots.

• The EXTRA_CFLAGS and EXTRA_AFLAGS makefile variables have been replaced with ccflags-y, ccflags-m, asflags-y, and asflags-m.

• kmem_cache_name(), which returned the name of a slab cache, has been removed from the kernel.

• The SLUB memory allocator now has a lockless fast path for allocations, speeding performance considerably. "Sadly this does nothing for the slowpath which is where the main issues with performance in slub are but the best case performance rises significantly."

• Kernel threads can be created on a specific NUMA node with the new kthread_create_on_node() function.

• The new function delete_from_page_cache() does what its name implies; unlike remove_from_page_cache() (which has now been deleted), it also decrements the page's reference count. It thus more closely mirrors add_to_page_cache().

• There is a whole new set of functions which are the preferred way to convert strings to integer values; see this article for details.

• The new "hwspinlock" framework allows the implementation of synchronization primitives on systems where different cores are running different operating systems. See Documentation/hwspinlock.txt for more information.

If the usual two-weeks rule holds, the 2.6.39 merge window can be expected to close on March 28. Watch this space next week for a summary of the final changes merged for this development cycle.