Messages in this thread | | | Date | Fri, 7 Dec 2012 16:57:27 -0500 | From | Theodore Ts'o <> | Subject | Re: [PATCH, 3.7-rc7, RESEND] fs: revert commit bbdd6808 to fallocate UAPI |
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On Fri, Dec 07, 2012 at 04:42:06PM -0500, Ric Wheeler wrote: > The other things that I think we should try would be to convert over > larger chunks as we discussed on the list back in the summer (just > because the user writes 4KB does not mean that we cannot flip over > 1MB and zero that).
Writing a megabyte is not free. If you assume that your HDD has a sustained write throughput of 100-125 MB/s, writing a megabyte will take 8-10ms. It might be a win if you amortize it over a large number of writes, but it doesn't help your 99.9 percentile latency numbers. (99.9 percentile latency numbers matters because eventually you'll have a user request which hits multiple serial long latency operations, and then the delay looks **really** user visible.)
- Ted
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