>>>>>> Thanks for your suggestion. I'll use TRACE_EVENT instead. >>>>> blk_add_trace_msg() supports both blktrace and tracepoints. I can >>>>> get messages from dm-ioband through debugfs. Could you expain why >>>>> should we use TRACE_EVENT instead? >>>>> >>>> Actually blk_add_trace_msg() has nothing to do with tracepoints.. >>>> >>>> If we use blk_add_trace_msg() is dm, we can use it in md, various block >>>> drivers and even ext4. So the right thing is, if a subsystem wants to add >>>> trace facility, it should use tracepoints/TRACE_EVENT. >>>> >>>> With TRACE_EVENT, you can get output through debugfs too, and it can be used >>>> together with blktrace: >>>> >>>> # echo 1 > /sys/block/dm/trace/enable >>>> # echo blk > /debugfs/tracing/current_tracer >>>> # echo dm-ioband-foo > /debugfs/tracing/tracing/set_event >>>> # cat /deubgfs/tracing/trace_pipe >>>> >>>> And you can enable dm-ioband-foo while disabling dm-ioband-bar, and you can >>>> use filter feature too. >>> Thanks for explaining. >>> The base kernel of current dm tree (2.6.30-rc4) has not supported >>> dm-device tracing yet. I'll consider using TRACE_EVENT when the base >>> kernel supports dm-device tracing. >>> >> I think we don't have any plan on dm-device tracing support, do we? And you >> don't need that. >> >> I downloaded dm-ioband 1.10.4, and applied it to latest tip-tree, and made >> a patch to convert those blktrace msgs to trace events. >> >> # ls /debug/tracing/events/dm-ioband >> enable ioband_endio ioband_issue_list ioband_urgent_bio >> filter ioband_hold_bio ioband_make_request >> # echo 1 /debug/tracing/events/dm-ioband/enable >> # echo blk /debug/tracing/current_tracer >> ... > > Is the following line unnecessary in the latest tip-tree? > > # echo 1 > /sys/block/dm/trace/enable > Yes, still needed. I was not giving a complete demonstration. ;) > How to enable/disable tracing on each device? echo 1 > /sys/block/dm-0/trace/enable echo 1 > /sys/block/dm-1/trace/enable Or use filter facility: echo "dev == $(( (ma0 << 20) | mi0 ))" > /debug/tracing/events/dm-ioband/filter This will filter out all events generated from dm-1, leaving those from dm-0. -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
