On Thu, Aug 16, 2012 at 10:07:29PM +1000, Joseph Glanville wrote: > There also seems to have been pretty severe performance regressions in > cache bypassed sequential I/O. > The newer code barely does 70mb/s sequential writes when > sequential_cuttoff is set to 4M however it does around 300mb/s when > set to 0 (no bypass) with dd and 1M block size. > When using the older codebase the cache bypass is actually slightly > faster than going to cache at around 360mb/s but this is still much > slower than the underlying block devices (as previously discussed).
Ouch. Can you try profiling it with perf while running dd? perf record -afg dd etc. etc. perf report should do it -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
