Messages in this thread | | | Date | Tue, 6 Feb 2007 16:44:43 -0800 | From | Joel Becker <> | Subject | Re: [PATCH 2 of 4] Introduce i386 fibril scheduling |
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On Tue, Feb 06, 2007 at 04:23:52PM -0800, Davide Libenzi wrote: > To how many "sessions" those 1000 *parallel* I/O operations refer to? > Because, if you batch them in an async fashion, they have to be parallel.
They're independant. Of course they have to be parallel, that's what I/O wants.
> Without the per-async operation status code, you'll need to wait a result > *for each* submitted syscall, even the ones that completed syncronously.
You are right, but it's more efficient in some cases.
> Open questions are: > > - Is the 1000 *parallel* syscall vectored submission case common?
Sure is for I/O. It's the majority of the case. If you have 1000 blocks to send out, you want them all down at the request queue at once, where they can merge.
> - Is it more expensive to forcibly have to wait and fetch a result even > for in-cache syscalls, or it's faster to walk the submission array?
Not everything is in-cache. Databases will be doing O_DIRECT and will expect that 90% of their I/O calls will block. Why should they have to iterate this list every time? If this is the API, they *have* to. If there's an efficient way to get "just the ones that didn't block", then it's not a problem.
Joel
--
"The real reason GNU ls is 8-bit-clean is so that they can start using ISO-8859-1 option characters." - Christopher Davis (ckd@loiosh.kei.com)
Joel Becker Principal Software Developer Oracle E-mail: joel.becker@oracle.com Phone: (650) 506-8127 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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