Messages in this thread | | | Date | Fri, 30 Jun 2006 11:24:57 -0700 | From | Joel Becker <> | Subject | Re: Proposal and plan for ext2/3 future development work |
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On Fri, Jun 30, 2006 at 10:13:06AM -0700, Badari Pulavarty wrote: > I tried adding "delayed allocation" for ext3 earlier. Yes. VFS level > infrastructure would be nice. But, I haven't found much that we can > do at VFS - which is common across all the filesystems (except > mpage_writepage(s) handling). Most of the stuff is specific to > filesystem implementation (even though it could be common) - coming > out with VFS level interfaces to suite all the different filesystem > delalloc would be *interesting* exercise.
Well, to be fair, I'm just going by what little I know about XFS. They maintain a cache of all pages waiting on delayed allocation for writepack. Why have this entire cache (hash, list, whatever) when we could create some state on in the pagecache? We save a large chunk of memory and some complex writeback code. I suspect you were thinking of this when you said "mpage_writepage(s) handling". But this is a large complexity win if we can do it. The same with metadata/data ordering issues. ie, data=ordered or even plain "creat(2); write(2)". I don't know how generic the ordering is for each filesystem, but there is always room for play. On-disk, of course each filesystem is going to be different. I'm not sure we could fit a fully-generic aops->reserve_space() & aops->commit_space() API. But I don't think we need to.
Joel --
"Well-timed silence hath more eloquence than speech." - Martin Fraquhar Tupper
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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