Re: [PATCH] PAGE_SIZE IO for RAW (RAW VARY)

[Alan Cox]

> Here is a 2.4.17 patch for doing PAGE_SIZE IO on raw devices. Instead 
> of doing 512 byte buffer heads, the patch does 4K buffer heads. This
> patch significantly reduced CPU overhead and increased IO throughput
> in our database benchmark runs. (CPU went from 45% busy to 6% busy).

Does that work out when the application is still doing 512 byte raw I/O.
Its fine to fall back to the current performance but at least one very
large competing database would get quite irate if the fallback made
512 byte mode slower or nonfunctional ?

Alan