On Mon, Jul 29, 2013 at 03:32:49PM +1200, Andrew Thrift wrote: > Hi, > > We are noticing some odd performance characteristics with bcache on > 3.10 Mainline kernel. > > We are using Intel DC S3700 SSD and Seagate Constellation ES.2 HDD > > Using FIO to perform a 4K random write test with QD=32 and 4 > instances we get: > > RAW SSD: 55.5K iops > > RAW HDD: 540 iops > > Fresh bcache on top of SSD/HDD [writeback]: 36.8K iops > > Which is not great, but OK. > > However if I run the FIO test a number of times, letting it write > out the data to the backing device after each run, after a few runs > I will notice the IOPS drop. When the benchmark starts it will sit > around 14K IOPS, then as soon as it starts writing to the backing > device this will drop to around 5K IOPS. On the subsequent runs it > will never go above 5K IOPS. > > > > Has there been a performance regression on 3.10 ? I don't seem to be able to reproduce this in the bcache-testing branch (but I haven't tried stock 3.10, and also the SSD in my test machine isn't near as fast as yours). Could you try the testing branch and see if you can reproduce it there? -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
