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Badari Pulavarty <pbadari@us.ibm.com> wrote: > > I am trying to speed up ext3 writepage() by avoiding > journaling in non-block allocation cases. Does this > look reasonable ? So far, my testing is fine. What am > I missing here ? Nothing. ext3's writepage(), prepare_write() and commit_write() do often needlessy open and close transactions when we're doing overwrites. It's something I've meant to look at for a few years, on and off. I'd expect that prepare_write() and commit_write() are more important than writepage(). It might be better to test PageMappedToDisk() rather than walking the buffers. It's certainly faster and it makes optimisation of prepare_write() and commit_write() easier to handle. I'm not sure that PageMappedToDisk() gets set in all the right places though - it's mainly for the `nobh' handling and block_prepare_write() would need to be taught to set it. I guess that'd be a net win, even if only ext3 uses it.. Then again, we might be able to speed up block_prepare_write() if PageMappedToDisk(page). If we go this way we need to be very very careful to keep PG_mappedtodisk coherent with the state of the buffers. Tricky. We need to think about whether block_truncate_page() should be clearing PG_mappedtoisk if we did a partial truncate. Don't forget that ext3 supports journalled-mode files on ordered- or writeback-mounted filesystems, via `chattr +j'. Please be sure to test the various combinations which that allows when playing with the write paths - it can trip things up. Also be sure to test nobh-mode. - 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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