After making headlines with its unexpectedly voluminous contributions to the Linux kernel in 2012, Microsoft has all but disappeared from the Linux development scene, according the latest report from the Linux Foundation.

The last edition of the Foundation's annual Linux kernel development report saw Microsoft break into the top 20 companies to have made kernel contributions, at number 17. That meant Redmond contributed around 1 per cent of all changes during the period studied. In this year's report, however, Microsoft is nowhere to be found.

That's not entirely surprising, given that Redmond's contributions logged in the 2012 report were almost entirely devoted to adding support for Microsoft technologies to the Linux kernel. Specifically, Microsoft maintains the kernel drivers for its Hyper-V virtualization hypervisor, which consist of tens of thousands of lines of code.

Outside of that work, Microsoft was never a particularly significant contributor to the kernel. In the Linux Foundation's 2012 report, Red Hat, Intel, Novell, and IBM each submitted far more changes than Redmond did, with those four companies combined accounting for 25.9 per cent of all kernel development.

That pattern repeated itself in this year's report, with Red Hat, Intel, Suse (now part of Attachmate, rather than Novell), and IBM together contributing 25.6 per cent of all kernel changes.

What was new this time around, however, was the expanded role that mobile chipmakers and developers played in kernel development, compared to last year. Freescale, Linaro, Samsung, and Texas Instruments all increased their activity during the period, while Nvidia, Qualcomm, and ARM – all absentees from last year's list – made the top 30 this time. Together, these companies contributed 15 per cent of all kernel code changes.

Unsurprisingly, perhaps, Nokia – which had contributed 1.9 per cent of all contributions in the Linux Foundation's 2012 report – also dropped off this year's list, much like Microsoft.

Corporate code contributions do make up the majority of Linux kernel development these days, and have done so for some time. But the largest single slice of the pie still comes from unaffiliated developers, who contributed 13.6 per cent of all code changes this time around. That's down from previous years, though; in the 2012 report, indie developers contributed 16.2 per cent of the code.

Another 3.3 per cent of contributions came from developers with "unknown" affiliations in the 2013 report, down from 4.3 per cent last year.

Amid all of these contributions, the Linux kernel is growing larger and the pace of its development is moving faster than ever before. In the 2012 report, Linux kernel 3.2 – the most recent version, at the time – comprised 37,626 files and 15 million lines of code. Today, kernel 3.10 is made up of 43,029 files and 17 million lines of code.

Similarly, a whopping 13,367 patches went into the 3.10 kernel – around nine changes per hour, averaged over the 63-day development cycle – beating the previous record of 12,394 patches in kernel 3.8. Only 11,780 patches went into kernel 3.2 (though that's obviously still nothing to sneeze at).

"This rate of change continues to increase, as does the number of developers and companies involved in the process," the Linux Foundation writes in its report. "Thus far, the development process has proved that it is able to scale up to higher speeds without trouble." ®