Messages in this thread | | | Date | Thu, 2 Nov 2017 14:36:23 -0600 | From | Mathieu Poirier <> | Subject | Re: [PATCH 13/17] coresight etr: Do not clean ETR trace buffer |
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On Thu, Oct 19, 2017 at 06:15:49PM +0100, Suzuki K Poulose wrote: > We zero out the entire trace buffer used for ETR before it > is enabled, for helping with debugging. Since we could be > restoring a session in perf mode, this could destroy the data.
I'm not sure to follow you with "... restoring a session in perf mode ...". When operating from the perf interface all the memory allocated for a session is cleanup after, there is no re-using of memory as in sysFS.
> Get rid of this step, if someone wants to debug, they can always > add it as and when needed. > > Cc: Mathieu Poirier <mathieu.poirier@linaro.org> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com> > --- > drivers/hwtracing/coresight/coresight-tmc-etr.c | 7 ++----- > 1 file changed, 2 insertions(+), 5 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-tmc-etr.c b/drivers/hwtracing/coresight/coresight-tmc-etr.c > index 31353fc34b53..849684f85443 100644 > --- a/drivers/hwtracing/coresight/coresight-tmc-etr.c > +++ b/drivers/hwtracing/coresight/coresight-tmc-etr.c > @@ -971,8 +971,6 @@ static void tmc_etr_enable_hw(struct tmc_drvdata *drvdata, > return; > > drvdata->etr_buf = etr_buf; > - /* Zero out the memory to help with debug */ > - memset(etr_buf->vaddr, 0, etr_buf->size);
I agree, this can be costly when dealing with large areas of memory.
> > CS_UNLOCK(drvdata->base); > > @@ -1267,9 +1265,8 @@ int tmc_read_unprepare_etr(struct tmc_drvdata *drvdata) > if (drvdata->mode == CS_MODE_SYSFS) { > /* > * The trace run will continue with the same allocated trace > - * buffer. The trace buffer is cleared in tmc_etr_enable_hw(), > - * so we don't have to explicitly clear it. Also, since the > - * tracer is still enabled drvdata::buf can't be NULL. > + * buffer. Since the tracer is still enabled drvdata::buf can't > + * be NULL. > */ > tmc_etr_enable_hw(drvdata, drvdata->sysfs_buf); > } else { > -- > 2.13.6 >
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