Jonathan Corbet, co-author of Linux Device Drivers, analyzed Linux changes over the past year and makes some predictions for the future.
Just when you think you understand Linux development, along comes something new. “There are no roadmaps in kernel land,” says Jonathan Corbet, co-author of Linux Device Drivers and the One Laptop Per Child project’s camera driver, and editor of the popular Linux site LWN.
“A lot of what’s going to be in future kernels is already out there if you know where to look for it,” Corbet explained at the Embedded Linux Conference Wednesday in Santa Clara, Calif.
Linux’s “git” revision control system allows for fine-grained tracking of contributions, by developer and — when you match developers to employers — by organization. “At a minimum, two-thirds of the changes in the kernel are being done by people being paid to do it,” Corbet said. He still lists about a quarter of kernel contributions as unknown, because they haven’t been clearly identified as either volunteer or done on behalf of a company.
Red Hat developers account for 14% of kernel changes in the past year, known volunteers are at 12%, and IBM and Novell come in with 8% and 4%, respectively. A total of 2074 developers have contributed, and only 10 of them count for more than 1% of changes each, Corbet said.
Although kernel releases have been changing only in the third decimal place, and no 2.7 development has started, “Every 2.6 release is a major release, with API changes,” Corbet said. Among the, “really fundamental changes” introduced in the past year are:
* 2.6.16 OCFS2: Oracle’s clustered filesystem
* 2.6.17 SPARC Niagra support, Broadcom 43xx wireless driver
* 2.6.18 A fundamental change to how interrupts are handled
* 2.6.19 Red Hat’s GFS2 cluster filesystem
* 2.6.20 Common virtualization infrastructure: paravirt_ops. Kernel Virtual Machine (KVM).
The current development kernel, due for release shortly, will add a power-saving feature called “dynamic tick,” which replaces a regular timer interrupt with one that goes off only when work is scheduled to be done. “It’s useful in any situation where you’re concerned about power management,” Corbet said. The One Laptop Per Child project, which is at the cutting edge of power savings on the desktop, wants this feature, as do operators of systems that host many virtualized guests.
Virtualization has many contending projects, but kernel developers are making them settle some technical beefs in order to get kernel support. “The kernel developers have no interest in adding hypervisor hooks for several virtualization systems,” Corbet said. A common hypervisor interface, called paravirt_ops, is now part of the kernel. Although Xen made it into both SuSE Linux Enterprise Server and Red Hat Enterprise Linux, the new KVM beat it into the mainstream kernel. “Xen really risks being upstaged by other developments that are going on,” Corbet said.
Kernel developer Valerie Henson has brought attention to a coming storage crisis: disks are quickly getting bigger, but they are getting faster much less quickly, and they are not getting any more reliable.
The large RAID array at kernel.org recently took an entire week to check using the “fsck” program, Corbet said. A promising approach is to split filesystems into chunks, to avoid running fsck on the whole filesystem at once. “I don’t think you’ll see anything like ZFS in the near future,” Corbet said. ZFS, Sun’s advanced filesystem for Solaris, combines the functionality that in Linux is handled by software raid, logical volume management and the filesystem itself.
Device driver support is improving, but the main obstacle seems to be that some vendors don’t yet understand the process for Linux support. “There’s a lot of just plain the hardware vendors don’t get it yet,” Corbet said. Support for Broadcom network hardware is already in the kernel, and a “legal cloud” over OpenBSD’s Atheros driver has been dispelled, Corbet said.
Intel is setting the standard for 3D graphics support, alhough the company’s graphics hardware is only available integrated into the motherboard. “You can’t buy a separate graphics card, for now. I assume this is coming,” Corbet said. Other vendors’ hardware is getting independent support. NVIDIA is “not helpful,” Corbet said, but a project called Nouveau has “serious momentum” and is already running some 3D graphics demos. “A lot of people are hoping that once the AMD acquisition goes through that AMD will talk some sense into them,” he added.
Proprietary device drivers aren’t working, Corbet said as he showed a text-filled slide full of reasons. “It’s not a way we can go, we cannot give in to it, and I don’t think we’re going to have to.”
