On Fri, Oct 25 2013 at 4:13pm -0400,
Alasdair G Kergon <agk@xxxxxxxxxx> wrote:
> On Thu, Oct 24, 2013 at 02:30:34PM -0400, Mike Snitzer wrote:
> > From: Morgan Mears <morgan.mears@xxxxxxxxxx>
>
> > This commit includes a non-terminal policy (aka "shim") called trc that
> > may be stacked ontop of a terminal policy (e.g. mq).
> > The second shim, trc, adds function-call-level tracing to the policy
> > stack. By default, an INFO-level log message including function name
> > and parameter(s) will be generated whenever most of the cache policy
> > interface functions are called. An interface to increase or decrease
> > the verbosity of the trace output is also provided.
>
> Firstly, why not call it 'trace' in full, rather than abbreviating it to 3
> consonants?
We can easily rename.
> > +++ b/drivers/md/dm-cache-policy-trc.c
>
> > +#define DM_TRC_OUT(lev, p, f, arg...) \
> > + do { \
> > + if (to_trc_policy(p)->trace_level >= lev) \
> > + DMINFO("%s: " f, __func__, ## arg); \
> > + } while (0)
>
> OK for private debugging, but I can't pretend to be very keen on this
> one going upstream in this form. Might this not need to support high
> volumes of messages sometimes? Were other upstream mechanisms
> considered? (E.g. see Documentation/trace).
Think this would take care of it (not full-blown tracepoints like
blktrace but certainly more performant than standard printk):
---
drivers/md/dm-cache-policy-trc.c | 2 +-
include/linux/device-mapper.h | 3 +++
2 files changed, 4 insertions(+), 1 deletion(-)
Index: linux/drivers/md/dm-cache-policy-trc.c
===================================================================
--- linux.orig/drivers/md/dm-cache-policy-trc.c
+++ linux/drivers/md/dm-cache-policy-trc.c
@@ -27,7 +27,7 @@
#define DM_TRC_OUT(lev, p, f, arg...) \
do { \
if (to_trc_policy(p)->trace_level >= lev) \
- DMINFO("%s: " f, __func__, ## arg); \
+ DMTRACE("%s: " f, __func__, ## arg); \
} while (0)
enum dm_trace_lev_e {
Index: linux/include/linux/device-mapper.h
===================================================================
--- linux.orig/include/linux/device-mapper.h
+++ linux/include/linux/device-mapper.h
@@ -520,6 +520,9 @@ extern struct ratelimit_state dm_ratelim
"\n", ## arg); \
} while (0)
+#define DMTRACE(f, arg...) \
+ trace_printk(DM_NAME ": " DM_MSG_PREFIX ": " f "\n", ## arg)
+
#ifdef CONFIG_DM_DEBUG
# define DMDEBUG(f, arg...) \
printk(KERN_DEBUG DM_NAME ": " DM_MSG_PREFIX " DEBUG: " f "\n", ## arg)
--
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