The Linux kernel: now and then

By Sam Varghese
Wednesday, 30 January 2008 16:00

Opinion and Analysis

Other well-known companies involved in funding included IBM (8 per cent), Novell (7 per cent), Intel (4 per cent), Oracle (2 per cent), Google (1 per cent) and SGI (1 per cent).

Corbet also charted the development periods from the first kernel to the 2.6.0 branch when major releases were made - the last change from 2.4.0 to 2.6.0 took nearly three years, whereas development time for earlier major versions was less.

These days, point releases are made and these happen much sooner. For instance, 2.6.24 has just been released and hence it is likely, given the existing schedule, that 2.6.25 would be released sometime in April, Corbet said.

The release cycle now generally includes a two-week period when changes are merged; there is then an eight to 12-week period when stabilisation work is carried out.

These days, given the number of developers contributing patches, there are a huge number that go in during each merge period, Corbet said.

The current merge window will close about two weeks from now, the delay being because Torvalds is attending the conference.

In April 2005, the kernel development was moved from a proprietary source code management system called BitKeeper to a system created by Torvalds and others named git.

From the time the git repository was used, Corbet said, there had been more or less a staircase pattern of development with the system of the two-week merge window beginning in April 2005.

And, to give an idea of the amount of work that goes in, he said that from 2.6.20 rc3 to 2.6.20 rc7, there were changes made to two million lines of code with 750,000 lines being added.

Looking at 2007, he said that 1900 developers had contributed code to the kernel and nearly 200 companies had been involved though only 11 contributed more than 1 per cent of the total.