Messages in this thread | | | Subject | Re: [RFC][WIP] DIO simplification and AIO-DIO stability | From | Badari Pulavarty <> | Date | Thu, 23 Feb 2006 16:39:26 -0800 |
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On Thu, 2006-02-23 at 12:59 +0530, Suparna Bhattacharya wrote: > DIO code complexity and stability concerns were discussed way back during > OLS and Kernel summit last year. Still, the lack of a solid alternative and > motivation to subject oneself to the test of courage and delicate balance > that fiddling with this code entails, has meant that gingerly applying fixes > and bandaids as and when bugs are found, and moving on thereafter, > continues to be the most palatable option. > > A recent AIO-DIO bug reported by Kenneth Chen, came very close > to being the proverbial last straw for me. Hence, here is a rough attempt to > put together a (currently WIP) draft towards DIO code simplication, based > on suggestions that some of you have brought up at various times. Several > details, e.g. range locking implementation still need to be fleshed out > completely, ideas/comments/suggestions would be welcome. > > http://www.kernel.org/pub/linux/kernel/people/suparna/DIO-simplify.txt > (also inlined below) > > It would be quite pointless (and painful!), if the rewrite ends up becoming > just as tricky and error prone as before. Such a patch will need a very > close critical review by many sharp eyes, to avoid disrupting the current > state of stability. So before going any further with this, I'm looking > for feedback along the lines of: > > - Is this a worthwhile thing to attempt ? Or is status quo good enough ? > - Does the approach make sense ? Is there a simpler way ? > - Is there any hidden complexity or performance overhead that you forsee ? > - Adding an extra tag to the radix-tree for locking a range of pages would > impact the size of the radix tree; would that be a concern ?
I am still trying to understand the whole proposal to give you better feedback. But, my gut feeling is - its not going to be any more simpler than what we have today :(
Andrew did an excellent job when he started (with the set of requirements we had at that time). Then we started adding more and more features/corner-case fixes/functionality/locking fixes/error handling cases etc - which added all the complexity.
I think it deserves a cleanup, but afraid to touch it - since its going to take few months to stabilize it and get it right. We need to collect all the test cases before undertaking this.
Thanks, Badari
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