Messages in this thread |  | | Date | Tue, 6 Feb 2001 13:54:45 -0500 (EST) | From | Ben LaHaise <> | Subject | Re: [Kiobuf-io-devel] RFC: Kernel mechanism: Compound event wait |
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On Tue, 6 Feb 2001, Ingo Molnar wrote:
> If you are merging based on (device, offset) values, then that's lowlevel > - and this is what we have been doing for years. > > If you are merging based on (inode, offset), then it has flaws like not > being able to merge through a loopback or stacked filesystem.
I disagree. Loopback filesystems typically have their data contiguously on disk and won't split up incoming requests any further.
Here are the points I'm trying to address:
- reduce the overhead in submitting block ios, especially for large ios. Look at the %CPU usages differences between 512 byte blocks and 4KB blocks, this can be better. - make asynchronous io possible in the block layer. This is impossible with the current ll_rw_block scheme and io request plugging. - provide a generic mechanism for reordering io requests for devices which will benefit from this. Make it a library for drivers to call into. IDE for example will probably make use of it, but some high end devices do this on the controller. This is the important point: Make it OPTIONAL.
You mentioned non-spindle base io devices in your last message. Take something like a big RAM disk. Now compare kiobuf base io to buffer head based io. Tell me which one is going to perform better.
-ben
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