Merging the virtual memory work [LWN.net]

The LWN Kernel Page has included several articles over the last month on the work to improve the scalability of the virtual memory subsystem by eliminating the reverse mapping chains currently used by the 2.6 kernel. That work reached a milestone on March 26, when Andrea Arcangeli released 2.6.5-rc2-aa3 with more virtual memory changes and a comment:

Ok, this seems feature complete. Both nonlinear swapping and prio_tree are available now. I believe objrmap-core+anon-vma+prio_tree can be merged into mainline after a bit more of testing, certainly they looks good enough for -mm.

Andrea raised the issue again when he released 2.6.5-rc3-aa1. Andrew Morton finally replied at that point:

It's a bit early for that, I feel. I'd like to see thing settle down a little more at your end first, then see that Rajesh, Hugh and if possible Ingo have had a good go through everything.

And then there are the mechanics of swallowing a largely-undocumented 4,600-line patch which touches 60 files and tosses 30-odd rejects across 16 files.

It is not surprising that Andrew would hesitate to rush into merging major virtual memory changes in the middle of a stable kernel series. Most 2.6 users will, one imagines, be relieved to see that some caution is being applied here - regardless of the eventual value of this work. Andrea, however, is in more of a hurry: "Keep in mind this whole thing is going in production in a matter of a week, so please test and review now." Those words suggest that SUSE Linux 9.1 will include the new VM code. One can only hope that Andrea's high level of confidence in that code is justified.

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