On 4/5/13 12:23 PM, Jeff Davis wrote:
Are you still looking into SIMD? Right now, it's using the existing CRC implementation. Obviously we can't change it after it ships. Or is it too late to change it already?
Simon just headed away for a break, so I'll try to answer this. He committed with the truncated WAL CRC to get the feature in with as few changes as possible. The idea was to see if any more serious problems fell out ASAP, before getting any deeper in to adding more code for optimization. The issues already spotted by Fujii Masao and Jeff Janes suggest that was a good choice.
Since this is a initdb time change and not in the field yet, in theory changes to the CRC method used could go along with a catversion bump. At the point in the 9.3 release cycle where those stop being acceptable then it's definitely too late. That's not quite yet though. Doing some more tuning to make this feature faster during the alpha period is something I would like to see the project consider.
I'm gearing up right now to help do more testing of the various options that Ants has been generated. This week's progress was getting a good AMD based system into my test farm, along with one of Seagate's new drives with a built-in BBWC. (Their latest SSHD flash hybrid model caches writes with a capacitor for clean shutdown on power loss)
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