On 4/30/20 5:47 AM, Jan Kara wrote: > Hello, > > I was investigating a performance issue with BFQ IO scheduler and I was > pondering why I'm not seeing informational messages from BFQ. After quite > some debugging I have found out that commit 35fe6d763229 "block: use > standard blktrace API to output cgroup info for debug notes" broke standard > blktrace API - namely the informational messages logged by bfq_log_bfqq() > are no longer displayed by blkparse(8) tool. This is because these messages > have now __BLK_TA_CGROUP bit set and that breaks flags checking in > blkparse(8). It isn't that hard to fix blkparse once you know what the > problem is but I've wasted couple hours on this... > > Also apparently nobody tested the patch with blkparse(8) since 4.14 > days? Admittedly this requires CONFIG_BFQ_GROUP_IOSCHED and having cgroups > set up for the cgroup info to get emitted which probably is not that common > with non-production machines. > > Anyway, what to do now? Update blkparse(8) and hope nobody else is using > the blktrace API (likely I'd say)? Revert the change? It's been this long and nobody has complained, I think we should just update blkparse. -- Jens Axboe
