KernelNewbies:

Summary: Linux 4.4 has not been released

1. Prominent features

1.1. TCP listener handling completely lockless, which make possible faster and more scalable TCP servers

In this release, and as a result from an effort that started two years ago, the TCP implementation has been refactored to make the TCP listener fast path completely lockless. During tests, a server was able to process 3,500,000 SYN packets per second on one listener and still have available cpu cycles - about 2 to 3 order of magnitude what it was possible before. SO_REUSEPORT has also been extended (see Networking section) to add proper cpu/numa affinities, so that heavy duty TCP servers can get proper siloing thanks to multi-queues NICs.

Code: [https://git.kernel.org/torvalds/c/4d54d86546f62c7c4a0fe3b36a64c5e3b98ce1a9 commit], [https://git.kernel.org/torvalds/c/e6934f3ec00b04234acb24a1a2c28af59763d3b5 commit], [https://git.kernel.org/torvalds/c/c3fc7ac9a0b978ee8538058743d21feef25f7b33 commit]

1.2. Faster and leaner loop device with Direct I/O and Asynchronous I/O support

This release introduces support of Direct I/O and asynchronous I/O for the loop block device. There are several advantages to use direct I/O and AIO on read/write loop's backing file: double cache is avoided due to Direct I/O which reduces memory usage a lot; unlike user space direct I/O there isn't cost of pinning pages; avoids context switches in some cases because concurrent submissions can be avoided. See commits for benchmarks.

Code: [https://git.kernel.org/torvalds/c/ab1cb278bc7027663adbfb0b81404f8398437e11 commit], [https://git.kernel.org/torvalds/c/2e5ab5f379f96a6207c45be40c357ebb1beb8ef3 commit], [https://git.kernel.org/torvalds/c/5b5e20f421c0b6d437b3dec13e53674161998d56 commit], [https://git.kernel.org/torvalds/c/bc07c10a3603a5ab3ef01ba42b3d41f9ac63d1b6 commit], [https://git.kernel.org/torvalds/c/e03a3d7a94e2485b6e2fa3fb630b9b3a30b65718 commit]

1.3. 3D support in virtual GPU driver

virtio-gpu is a driver for virtualization guests that allows to use the host graphics card efficiently. In this release, it allows the virtualization guest to use the capabilities of the host GPU to accelerate 3D rendering. In practice, this means that a virtualized linux guest can run a opengl game while using the GPU acceleration capabilities of the host, as show in [https://www.youtube.com/watch?v=ONFGnUaln-4 this] or [https://www.youtube.com/watch?v=ZuuF092RDDc this] video. This also requires running [http://wiki.qemu.org/ChangeLog/2.5#virtio QEMU 2.5].

[Outdated project page https://virgil3d.github.io/]

[https://www.youtube.com/watch?v=rPeMrmeLTig 44m linux.conf talk about the project]

Code: [https://git.kernel.org/torvalds/c/3187567222178d4b3742e88242f7abb3c3b7a215 commit]

1.4. Journalled RAID5 MD support

This release adds journalled raid5 support to the MD (RAID/LVM) layer. With a journal device configured (typically NVRAM or SSD), Data/parity writing to raid array first writes to the log, then write to raid array disks. If crash happens, we can recovery data from the log. This can speed up raid resync and fixes RAID5 write hole issue - a crash during degraded operations cannot result in data corruption. In future releasees the journal will also be used to improve performance and latency

Code: [https://git.kernel.org/torvalds/c/ac322de6bf5416cb145b58599297b8be73cd86ac merge]

1.5. Unprivileged eBPF

eBPF programs got its own syscall in [http://kernelnewbies.org/Linux_3.18#head-ead251efb6bbdbe2922e7c6bd0c7b46342e03dad Linux 3.18], but until now its use had been restricted to root, because these programs were dangerous for security. eBPF programs are, however, validated by the kernel, and in this release the eBPF verifier has been improved and unprivileged users can use it (although unprivileged eBPF is only meaningful for 'socket filter'-like programs, eBPF programs for tracing and TC classifiers/actions will stay root only). This feature can be switched off with the sysctl kernel.unprivileged_bpf_disabled (once true, bpf programs and maps cannot be accessed from unprivileged process, and the toggle cannot be set back to false)

Recommended LWN article: [http://lwn.net/Articles/660331/ Unprivileged bpf()]

Code: [https://git.kernel.org/torvalds/c/1be7f75d1668d6296b80bf35dcf6762393530afc commit], [https://git.kernel.org/torvalds/c/aaac3ba95e4c8b496d22f68bd1bc01cfbf525eca commit]

1.6. Block polling support

This release adds basic support for polling for specific IO to complete, which can improve latency and throughput in very fast devices. Currently O_DIRECT sync read/write are supported. This support is only intended for testing, in future releases stats tracking will be used to auto-tune this. For now, for benchmark and testing purposes, we add a sysfs file (io_poll) that controls whether polling is enabled or not.

Recommended LWN article: [http://lwn.net/Articles/663879/ Block-layer I/O polling]

Code: [https://git.kernel.org/torvalds/c/15c4f638f3d41bae52105ca4c0c8760afbcbeaab commit], [https://git.kernel.org/torvalds/c/05229beeddf7e75e2e616ddaad4b70e7fca9528d commit], [https://git.kernel.org/torvalds/c/a0fa9647a54e81883abd57c5c865d1747f68a577 commit]

2. Drivers and architectures

3. Core (various)

4. File systems

5. Memory management

6. Block layer

7. Cryptography

crypto: caam - add support for acipher xts(aes) [https://git.kernel.org/torvalds/c/c6415a6016bff0b547c13cadb1d5e50e9ace2be3 commit] crypto: keywrap - add key wrapping block chaining mode [https://git.kernel.org/torvalds/c/e28facde3c39005071cc5323d56539bb44efa446 commit] crypto: qat - add support for ctr(aes) and xts(aes) [https://git.kernel.org/torvalds/c/def14bfaf30d5d5a4a8fe5bf600ce09232e688c0 commit]

8. Security

9. Tracing and perf tool

10. Virtualization

11. Networking

TODO

12. Other news sites

KernelNewbies: Linux_4.4 (last edited 2016-01-10 20:13:50 by diegocalleja)