Messages in this thread | | | Subject | Re: [RFC PATCH] block: Fix bio merge induced high I/O latency | From | Ben Gamari <> | Date | Sat, 17 Jan 2009 15:03:46 -0500 |
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On Sat, 2009-01-17 at 11:26 -0500, Mathieu Desnoyers wrote: > This patch implements a basic test to make sure we never merge more than 128 > requests into the same request if it is the "last_merge" request. I have not > been able to trigger the problem again with the fix applied. It might not be in > a perfect state : there may be better solutions to the problem, but I think it > helps pointing out where the culprit lays.
Unfortunately, it seems like the patch hasn't really fixed much. After porting it forward to Linus' master, I haven't exhibited any difference in real world use cases (e.g. desktop use cases while building a kernel).
Given Jen's remarks, I suppose this isn't too surprising. Does anyone else with greater familiarity with the block I/O subsystem have any more ideas about the source of the slowdown? It seems like the recent patches incorporating blktrace support into ftrace could be helpful for further data collection, correct?
- Ben
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