Re: [PATCH 5/5] blktrace: print human-readable act_mask

Ingo Molnar
2009-03-24T08:39:41Z

* Li Zefan <lizf@cn.fujitsu.com> wrote:

> Print stringified act_mask instead of hex value:
> # cat act_mask
> read,write,barrier,sync,queue,requeue,issue,complete,fs,pc,ahead,meta,
> discard,drv_data
> # echo "meta,write" > act_mask
> # cat act_mask
> write,meta

Nice!

It would also be nice to activate trace filters for the blktrace
tracepoints - i.e. to convert them to the TRACE_EVENT() enumeration
format. Beyond user-space parseable field enumeration and filter,
that will also speed up tracing and allows binary record streaming
with splice() zero-copy.

Via that "act_mask" can become a filterable field and you can define
expressions to filter. All other fields like sector become in-kernel
filterable too.

See a few examples here:

include/trace/irq_event_types.h
include/trace/sched_event_types.h

Note, blktrace tracepoints are certainly more complex than the
tracepoints above - you can embedd C statements in TRACE_EVENT()'s
TP_fast_assign() bit.

It was specifically designed to allow the support of blktrace
tracepoints, so you can embedd the blk_pc_request() and disk_devt()
translation for the block_rq_complete event or
block_rq_requeue/issue tracepoints.

> +static struct {
> + int mask;
> + const char *str;
> +} mask_maps[] = {
> + { BLK_TC_READ, "read" },
> + { BLK_TC_WRITE, "write" },
> + { BLK_TC_BARRIER, "barrier" },
> + { BLK_TC_SYNC, "sync" },
> + { BLK_TC_QUEUE, "queue" },
> + { BLK_TC_REQUEUE, "requeue" },
> + { BLK_TC_ISSUE, "issue" },
> + { BLK_TC_COMPLETE, "complete" },
> + { BLK_TC_FS, "fs" },
> + { BLK_TC_PC, "pc" },
> + { BLK_TC_AHEAD, "ahead" },
> + { BLK_TC_META, "meta" },
> + { BLK_TC_DISCARD, "discard" },
> + { BLK_TC_DRV_DATA, "drv_data" },
> +};

(minor nit: this should be a const.)

Jens, Arnaldo, Steve, the series from Li looks good to me - Ack?

Ingo