Re: [PATCH v4 06/21] perf arm-spe: Refactor printing string to buffer
Hi Dave,
On Tue, Oct 27, 2020 at 02:31:54PM +, Dave Martin wrote:
> On Tue, Oct 27, 2020 at 03:09:02AM +, Leo Yan wrote:
> > When outputs strings to the decoding buffer with function snprintf(),
> > SPE decoder needs to detects if any error returns from snprintf() and if
> > so needs to directly bail out. If snprintf() returns success, it needs
> > to update buffer pointer and reduce the buffer length so can continue to
> > output the next string into the consequent memory space.
> >
> > This complex logics are spreading in the function arm_spe_pkt_desc() so
> > there has many duplicate codes for handling error detecting, increment
> > buffer pointer and decrement buffer size.
> >
> > To avoid the duplicate code, this patch introduces a new helper function
> > arm_spe_pkt_snprintf() which is used to wrap up the complex logics, and
> > the caller arm_spe_pkt_desc() will call it and simply check the returns
> > value.
> >
> > This patch also moves the variable 'blen' as the function's local
> > variable, this allows to remove the unnecessary braces and improve the
> > readability.
> >
> > Suggested-by: Dave Martin
> > Signed-off-by: Leo Yan
> > Reviewed-by: Andre Przywara
> > ---
> > .../arm-spe-decoder/arm-spe-pkt-decoder.c | 247 ++
> > 1 file changed, 135 insertions(+), 112 deletions(-)
> >
> > diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > index 04fd7fd7c15f..b400636e6da2 100644
> > --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> > @@ -9,6 +9,7 @@
> > #include
> > #include
> > #include
> > +#include
> >
> > #include "arm-spe-pkt-decoder.h"
> >
> > @@ -258,192 +259,214 @@ int arm_spe_get_packet(const unsigned char *buf,
> > size_t len,
> > return ret;
> > }
> >
> > +static int arm_spe_pkt_snprintf(char **buf_p, size_t *blen,
> > + const char *fmt, ...)
> > +{
> > + va_list ap;
> > + int ret;
> > +
> > + va_start(ap, fmt);
> > + ret = vsnprintf(*buf_p, *blen, fmt, ap);
> > + va_end(ap);
> > +
> > + if (ret < 0)
> > + return ret;
> > +
> > + *buf_p += ret;
> > + *blen -= ret;
> > + return ret;
> > +}
> > +
>
> This approach seems OK, though I wonder whether all the
> "if (ret < 0) return;" logic is really needed.
>
> In case of failure, it probably doesn't matter what ends up in buf.
> If not, we could just implement a cumulative error:
>
> static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen,
> {
>
> /* ... */
>
> if (ret < 0) {
> if (err && !*err)
> *err = ret;
> } else {
> *buf_p += ret;
> *blen -= ret;
> }
>
> return err ? *err : ret;
> }
>
> and just return the final value of err.
>
>
>
> > int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
> > size_t buf_len)
> > {
> > int ret, ns, el, idx = packet->index;
> > unsigned long long payload = packet->payload;
> > const char *name = arm_spe_pkt_name(packet->type);
> > + size_t blen = buf_len;
> >
> > switch (packet->type) {
> > case ARM_SPE_BAD:
> > case ARM_SPE_PAD:
> > case ARM_SPE_END:
> > - return snprintf(buf, buf_len, "%s", name);
> > - case ARM_SPE_EVENTS: {
> > - size_t blen = buf_len;
> > -
> > - ret = 0;
> > - ret = snprintf(buf, buf_len, "EV");
> > - buf += ret;
> > - blen -= ret;
> > + return arm_spe_pkt_snprintf(, , "%s", name);
> > + case ARM_SPE_EVENTS:
> > + ret = arm_spe_pkt_snprintf(, , "EV");
> > + if (ret < 0)
> > + return ret;
> > +
>
> ...
>
> Then this becomes
>
> case ARM_SPE_END:
> return arm_spe_pkt_snprintf(, , , "%s", name);
> case ARM_SPE_EVENTS:
> arm_spe_pkt_snprintf(, , , "%s", name);
>
> if (payload & 0x1)
> arm_spe_pkt_snprintf(, , , "
> EXCEPTION-GEN");
> if (payload & 0x2)
> arm_spe_pkt_snprintf(, , , " RETIRED");
>
> /* ... */
>
>
> This might be over-engineering, but it does help to condense the code.
I agree this approach is more neat; will follow it to refine code.
Thanks a lot for detailed explaination.
Leo
Re: [PATCH v4 06/21] perf arm-spe: Refactor printing string to buffer
On Tue, Oct 27, 2020 at 03:09:02AM +, Leo Yan wrote:
> When outputs strings to the decoding buffer with function snprintf(),
> SPE decoder needs to detects if any error returns from snprintf() and if
> so needs to directly bail out. If snprintf() returns success, it needs
> to update buffer pointer and reduce the buffer length so can continue to
> output the next string into the consequent memory space.
>
> This complex logics are spreading in the function arm_spe_pkt_desc() so
> there has many duplicate codes for handling error detecting, increment
> buffer pointer and decrement buffer size.
>
> To avoid the duplicate code, this patch introduces a new helper function
> arm_spe_pkt_snprintf() which is used to wrap up the complex logics, and
> the caller arm_spe_pkt_desc() will call it and simply check the returns
> value.
>
> This patch also moves the variable 'blen' as the function's local
> variable, this allows to remove the unnecessary braces and improve the
> readability.
>
> Suggested-by: Dave Martin
> Signed-off-by: Leo Yan
> Reviewed-by: Andre Przywara
> ---
> .../arm-spe-decoder/arm-spe-pkt-decoder.c | 247 ++
> 1 file changed, 135 insertions(+), 112 deletions(-)
>
> diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> index 04fd7fd7c15f..b400636e6da2 100644
> --- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> +++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
> @@ -9,6 +9,7 @@
> #include
> #include
> #include
> +#include
>
> #include "arm-spe-pkt-decoder.h"
>
> @@ -258,192 +259,214 @@ int arm_spe_get_packet(const unsigned char *buf,
> size_t len,
> return ret;
> }
>
> +static int arm_spe_pkt_snprintf(char **buf_p, size_t *blen,
> + const char *fmt, ...)
> +{
> + va_list ap;
> + int ret;
> +
> + va_start(ap, fmt);
> + ret = vsnprintf(*buf_p, *blen, fmt, ap);
> + va_end(ap);
> +
> + if (ret < 0)
> + return ret;
> +
> + *buf_p += ret;
> + *blen -= ret;
> + return ret;
> +}
> +
This approach seems OK, though I wonder whether all the
"if (ret < 0) return;" logic is really needed.
In case of failure, it probably doesn't matter what ends up in buf.
If not, we could just implement a cumulative error:
static int arm_spe_pkt_snprintf(int *err, char **buf_p, size_t *blen,
{
/* ... */
if (ret < 0) {
if (err && !*err)
*err = ret;
} else {
*buf_p += ret;
*blen -= ret;
}
return err ? *err : ret;
}
and just return the final value of err.
> int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
>size_t buf_len)
> {
> int ret, ns, el, idx = packet->index;
> unsigned long long payload = packet->payload;
> const char *name = arm_spe_pkt_name(packet->type);
> + size_t blen = buf_len;
>
> switch (packet->type) {
> case ARM_SPE_BAD:
> case ARM_SPE_PAD:
> case ARM_SPE_END:
> - return snprintf(buf, buf_len, "%s", name);
> - case ARM_SPE_EVENTS: {
> - size_t blen = buf_len;
> -
> - ret = 0;
> - ret = snprintf(buf, buf_len, "EV");
> - buf += ret;
> - blen -= ret;
> + return arm_spe_pkt_snprintf(, , "%s", name);
> + case ARM_SPE_EVENTS:
> + ret = arm_spe_pkt_snprintf(, , "EV");
> + if (ret < 0)
> + return ret;
> +
...
Then this becomes
case ARM_SPE_END:
return arm_spe_pkt_snprintf(, , , "%s", name);
case ARM_SPE_EVENTS:
arm_spe_pkt_snprintf(, , , "%s", name);
if (payload & 0x1)
arm_spe_pkt_snprintf(, , , "
EXCEPTION-GEN");
if (payload & 0x2)
arm_spe_pkt_snprintf(, , , " RETIRED");
/* ... */
This might be over-engineering, but it does help to condense the code.
[...]
Cheers
---Dave
[PATCH v4 06/21] perf arm-spe: Refactor printing string to buffer
When outputs strings to the decoding buffer with function snprintf(),
SPE decoder needs to detects if any error returns from snprintf() and if
so needs to directly bail out. If snprintf() returns success, it needs
to update buffer pointer and reduce the buffer length so can continue to
output the next string into the consequent memory space.
This complex logics are spreading in the function arm_spe_pkt_desc() so
there has many duplicate codes for handling error detecting, increment
buffer pointer and decrement buffer size.
To avoid the duplicate code, this patch introduces a new helper function
arm_spe_pkt_snprintf() which is used to wrap up the complex logics, and
the caller arm_spe_pkt_desc() will call it and simply check the returns
value.
This patch also moves the variable 'blen' as the function's local
variable, this allows to remove the unnecessary braces and improve the
readability.
Suggested-by: Dave Martin
Signed-off-by: Leo Yan
Reviewed-by: Andre Przywara
---
.../arm-spe-decoder/arm-spe-pkt-decoder.c | 247 ++
1 file changed, 135 insertions(+), 112 deletions(-)
diff --git a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
index 04fd7fd7c15f..b400636e6da2 100644
--- a/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
+++ b/tools/perf/util/arm-spe-decoder/arm-spe-pkt-decoder.c
@@ -9,6 +9,7 @@
#include
#include
#include
+#include
#include "arm-spe-pkt-decoder.h"
@@ -258,192 +259,214 @@ int arm_spe_get_packet(const unsigned char *buf, size_t
len,
return ret;
}
+static int arm_spe_pkt_snprintf(char **buf_p, size_t *blen,
+ const char *fmt, ...)
+{
+ va_list ap;
+ int ret;
+
+ va_start(ap, fmt);
+ ret = vsnprintf(*buf_p, *blen, fmt, ap);
+ va_end(ap);
+
+ if (ret < 0)
+ return ret;
+
+ *buf_p += ret;
+ *blen -= ret;
+ return ret;
+}
+
int arm_spe_pkt_desc(const struct arm_spe_pkt *packet, char *buf,
size_t buf_len)
{
int ret, ns, el, idx = packet->index;
unsigned long long payload = packet->payload;
const char *name = arm_spe_pkt_name(packet->type);
+ size_t blen = buf_len;
switch (packet->type) {
case ARM_SPE_BAD:
case ARM_SPE_PAD:
case ARM_SPE_END:
- return snprintf(buf, buf_len, "%s", name);
- case ARM_SPE_EVENTS: {
- size_t blen = buf_len;
-
- ret = 0;
- ret = snprintf(buf, buf_len, "EV");
- buf += ret;
- blen -= ret;
+ return arm_spe_pkt_snprintf(, , "%s", name);
+ case ARM_SPE_EVENTS:
+ ret = arm_spe_pkt_snprintf(, , "EV");
+ if (ret < 0)
+ return ret;
+
if (payload & 0x1) {
- ret = snprintf(buf, buf_len, " EXCEPTION-GEN");
- buf += ret;
- blen -= ret;
+ ret = arm_spe_pkt_snprintf(, , "
EXCEPTION-GEN");
+ if (ret < 0)
+ return ret;
}
if (payload & 0x2) {
- ret = snprintf(buf, buf_len, " RETIRED");
- buf += ret;
- blen -= ret;
+ ret = arm_spe_pkt_snprintf(, , " RETIRED");
+ if (ret < 0)
+ return ret;
}
if (payload & 0x4) {
- ret = snprintf(buf, buf_len, " L1D-ACCESS");
- buf += ret;
- blen -= ret;
+ ret = arm_spe_pkt_snprintf(, , " L1D-ACCESS");
+ if (ret < 0)
+ return ret;
}
if (payload & 0x8) {
- ret = snprintf(buf, buf_len, " L1D-REFILL");
- buf += ret;
- blen -= ret;
+ ret = arm_spe_pkt_snprintf(, , " L1D-REFILL");
+ if (ret < 0)
+ return ret;
}
if (payload & 0x10) {
- ret = snprintf(buf, buf_len, " TLB-ACCESS");
- buf += ret;
- blen -= ret;
+ ret = arm_spe_pkt_snprintf(, , " TLB-ACCESS");
+ if (ret < 0)
+ return ret;
}
if (payload & 0x20) {
- ret = snprintf(buf, buf_len, " TLB-REFILL");
- buf += ret;
- blen -= ret;
+ ret = arm_spe_pkt_snprintf(, , " TLB-REFILL");
+ if (ret < 0)
+ return ret;
}
if (payload &
