Hello, On Mon, Apr 25, 2011 at 10:58:27AM +0200, Tejun Heo wrote: > Eh, wasn't your optimization only applicable if flush is not > queueable? IIUC, what your optimization achieves is merging > back-to-back flushes and you're achieving that in a _very_ non-obvious > round-about way. Do it in straight-forward way even if that costs > more lines of code. To add a bit more, here, flush exclusivity gives you an extra ordering contraint that while flush is in progress no other request can proceed and thus if there's another flush queued, it can be completed together, right? If so, teach block layer the whole thing - let block layer hold further requests while flush is in progress and complete back-to-back flushes together on completion and then resume normal queue processing. Also, another interesting thing to investigate is why the two flushes didn't get merged in the first place. The two flushes apparently didn't have any ordering requirement between them. Why didn't they get merged in the first place? If the first flush were slightly delayed, the second would have been issued together from the beginning and we wouldn't have to think about merging them afterwards. Maybe what we really need is better algorithm than C1/2/3 described in the comment? What did sysbench do in the workload which showed the regression? A lot of parallel fsyncs combined with writes? Thanks. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
