On Mon, 15 Oct 2007 16:13:15 -0400 Rik van Riel <[EMAIL PROTECTED]> wrote:
> Since you have been involved a lot with ext3 development, > which kinds of workloads do you think will show a performance > degradation with Arjan's patch? What should I test? Gee. Expect the unexpected ;) One problem might be when kjournald is doing its ordered-mode data writeback at the start of commit. That writeout will now be higher-priority and might impact other tasks which are doing synchronous file overwrites (ie: no commits) or O_DIRECT reads or writes or just plain old reads. If the aggregate number of seeks over the long term is the same as before then of course the overall throughput should be the same, in which case the impact might only be upon latency. However if for some reason the total number of seeks is increased then there will be throughput impacts as well. So as a starting point I guess one could set up a copy-a-kernel-tree-in-a-loop running in the background and then see what impact that has upon a large-linear-read, upon a read-a-different-kernel-tree and upon some database-style multithreaded O_DIRECT reader/overwriter. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/