On 11/25/18 8:24 AM, Bari Antebi wrote: > To Whom It May Concern, > > I've noticed a bug in fio while testing it. I expected to receive > output similar to the expected output below for: "hexdump -n 4096 > /dev/nvme0n1" (considering the configuration file I've used that may > be found below). > > Expected output: > > 0000000 fdc6 a8a8 7190 0219 1fb8 9632 d9dd 1e64 > /* random data */ > 00004c0 d8a3 13fe aeec 0fb6 5b14 162e 0000 0000 > 00004d0 0000 0000 0000 0000 0000 0000 0000 0000 > * > 0001000 > > > However, the output I've received contained data after address 4cc > (which should have been filled with zeros until 1000 as far as I > understand, but as you can see 99a contains data. > > > 0000000 fdc6 a8a8 7190 0219 1fb8 9632 d9dd 1e64 > /* random data */ > 00004c0 d8a3 13fe aeec 0fb6 5b14 162e 0000 0000 > 00004d0 0000 0000 0000 0000 0000 0000 0000 0000 > * > 0000990 0000 0000 0000 0000 fdc6 a8a8 7190 0219 > > Config file: > > [global] > group_reporting=1 > filename=/dev/nvme0n1 > name=task_nvme0n1 > rw=write > bs=4096 > numjobs=1 > iodepth=32 > buffer_compress_chunk=4096 > buffer_compress_percentage=70 > cpus_allowed=0-8 > cpus_allowed_policy=split > direct=1 > ioengine=libaio > loops=1 > refill_buffers=0 > > [job empty] > size=4096 > > The version I ran is fio-3.11, but it seems the bug wasn't fixed in > the new version from a look at the code. > > I solved the issue locally & would like to send a pr for the fix. > The problem in the code maybe found in "lib/rand.c", at the function > "__fill_random_buf_percentage". > After fio finishes to write the random part, it should write the > remainder of "((unsigned long long)segment * (100 - percentage)) / > 100", > but currently it writes "this_len" zeros which seems wrong. > > My solution is to add a single line under line 168 (of the current fio > version). If it's possible I'd like to add the PR myself, it will be > my first contribution to any open source code :) > 168. buf += this_len; > 169. this_len = segment - this_len Please do! The best bug reports are those that come with an analysis of the issue, and even include a fix. You don't have to do a PR, you can just send a patch here as well. It should basically be as simple as making the edit in the file, then run git diff and send the output. When you do send a diff or PR, ensure that your full description from this email is included. That's very useful for the future. -- Jens Axboe
