Garrett: ext4, application expectations and power management [LWN.net]

Garrett: ext4, application expectations and power management

Posted Mar 16, 2009 10:52 UTC (Mon) by MathFox (guest, #6104)
In reply to: Garrett: ext4, application expectations and power management by mjthayer
Parent article: Garrett: ext4, application expectations and power management

Michael, Yes, the kernel could do it, but such a log would have to be written to disk... But then it would be more efficient to directly write that log directly to the file system.
You'll create similar issues wrt. performance and commit intervals with a kernel-based log, but with the added overhead of writing data twice.

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Garrett: ext4, application expectations and power management

Posted Mar 16, 2009 10:54 UTC (Mon) by mjthayer (guest, #39183) [Link] (1 responses)

Would that apply even if the blocks for the log were reserved in advance and their location known to the kernel?

Garrett: ext4, application expectations and power management

Posted Mar 16, 2009 10:55 UTC (Mon) by mjthayer (guest, #39183) [Link]

I will answer my own question - presumably yes, because the kernel can't assume that the filesystem does a simple block to disk mapping.