The conclusion of the 3.10 merge window
By the time Linus announced the 3.10-rc1 kernel, he had pulled just
short of 12,000 non-merge changesets into the mainline kernel. That makes
3.10 the busiest merge window ever, by over 1,000 patches. The list of
changes merged since the previous 3.10 merge
window summary is relatively small, but it includes some significant
changes. The most significant of those changes are:
- The bcache caching layer has been
merged. Bcache allows a fast device (like an SSD) to provide fast
caching in front of a slower device; it is designed for fast
performance given the constraints of contemporary solid-state
devices. See Documentation/bcache.txt
for more information.
- The on-disk representation of extents in Btrfs has been changed to
make the structure significantly smaller. "
In practice this results in a 30-35% decrease in the size of our extent tree, which means we COW less and can keep more of the extent tree in memory which makes our heavy metadata operations go much faster.
" It is an incompatible format change that must be explicitly enabled when the filesystem is created (or after the fact with btrfstune). - The MIPS architecture has gained basic support for virtualization with
KVM. MIPS kernels can also now be built using the new "microMIPS"
instruction set, with significant space savings.
- New hardware support includes Abilis TB10x processors, Freescale ColdFire 537x processors, Freescale M5373EVB boards, Broadcom BCM6362 processors, Ralink RT2880, RT3883, and MT7620 processors, and Armada 370/XP thermal management controllers.
Changes visible to kernel developers include:
- The block layer has gained basic power management support; it is
primarily intended to control which I/O requests can pass through to
a device while it is suspending or resuming. To that end,
power-management-related requests should be marked with the net
__REQ_PM flag.
- A lot of work has gone into the block layer in preparation for
"immutable biovecs," a reimplementation of the low-level structure
used to represent ranges of blocks for I/O operations. One of the key
advantages here seems to be that it becomes possible to create a new
biovec that contains a subrange of an existing biovec, leading to fast
and efficient request splitting. The completion of this work will
presumably show up in 3.11.
- The dedicated thread pool implementation used to implement writeback in the memory management subsystem has been replaced by a workqueue.
If this development cycle follows the usual pattern, the final 3.10 kernel
release can be expected in early July. Between now and then, though, there
will certainly be a lot of bugs to fix.
| Index entries for this article | |
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| Kernel | Releases/3.10 |