Hello, I am working on setting up bcache on Ubuntu 13.10 (with kernel 3.11.0-17) for read performance testing in writethrough mode. I've written a test script which uses dd to write data to the bcache device, read it back in, and then attempt to read it again (to measure cache speed): # write the data to the disk dd if=/dev/zero of=/path/to/bcache/mount/file.raw bs=512 count=2 # read the data (using iflag=nocache to make sure it gets into bcache's # cache and doesn't use the kernel's cache) dd if=/path/to/bcache/mount/file.raw of=/dev/null iflag=nocache # now perform the read, which should read from bcache's cache dd if=/path/to/bcache/mount/file.raw of=/dev/null iflag=nocache However, if I cat /sys/block/bcache0/bcache/cache/cache_available_percent before and after performing the read, the value is always 100. Would using iflag=direct be better than iflag=nocache in this case? Is there a better way to force data into the cache for this type of performance benchmarking? Thanks, Andrew Martin -- 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
