SplitLRU Patch in Kernel 2.6.28 – Must Have for MySQL and InnoDB

If you’re running MySQL with InnoDB and an in-memory buffer pool, and having paging issues, you probably should upgrade to 2.6.28 ASAP.

We’ve been running it for about three months now. We’re still not able to use 100% of the memory without paging – more like 95%. However, this is a vast improvement over only being able to use 70% of our memory a few months back.

Here is the changelog:

Split the LRU lists in two, one set for pages that are backed by real file
systems (“file”) and one for pages that are backed by memory and swap
(“anon”). The latter includes tmpfs.

The advantage of doing this is that the VM will not have to scan over lots
of anonymous pages (which we generally do not want to swap out), just to
find the page cache pages that it should evict.

This patch has the infrastructure and a basic policy to balance how much
we scan the anon lists and how much we scan the file lists. The big
policy changes are in separate patches.

  1. joe

    You should probably contact Rik Van Riel or post on LKML. I bet they’re very interested in your findings.

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