Now that we can denote which bitmasks are cpumasks, it makes sense to
pretty-print them to a more user-friendly format: a cpulist.
There's two hurdles to that:
1) Estimating the required string buffer size.
I've tried to condense it down to an estimator function that is
computationally simple enough, though it overestimates by ~1/3.
For reference, this estimates:
180 bytes for NR_CPUS=64 (x86 defconfig)
911 bytes for NR_CPUS=256 (arm64 defconfig)
2) Iterating through the bits and bytes.
The kernel has a collection of carefully crafted bitmask iterators which
make this relatively simple (cf. bitmap_list_string()), but I didn't
feel justified in importing half a dozen helpers just for one function.
I've implemented a "homegrown" byte-parsing logic which isn't the
fastest, but is at least condensed to a single function.
Signed-off-by: Valentin Schneider <vschneid@xxxxxxxxxx>
---
src/event-parse.c | 168 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 167 insertions(+), 1 deletion(-)
diff --git a/src/event-parse.c b/src/event-parse.c
index ba8e727..d1363a5 100644
--- a/src/event-parse.c
+++ b/src/event-parse.c
@@ -4491,6 +4491,161 @@ static void print_bitmask_to_seq(struct tep_handle *tep,
free(str);
}
+#define log10(n) \
+( \
+ n < 10UL ? 0 : \
+ n < 100UL ? 1 : \
+ n < 1000UL ? 2 : \
+ n < 10000UL ? 3 : \
+ n < 100000UL ? 4 : \
+ n < 1000000UL ? 5 : \
+ n < 10000000UL ? 6 : \
+ n < 100000000UL ? 7 : \
+ n < 1000000000UL ? 8 : \
+ 9 \
+)
+
+/* ilog10(0) should be 1 but the 0 simplifies below math */
+#define ilog10(n) \
+( \
+ n == 0 ? 0UL : \
+ n == 1 ? 10UL : \
+ n == 2 ? 100UL : \
+ n == 3 ? 1000UL : \
+ n == 4 ? 10000UL : \
+ n == 5 ? 100000UL : \
+ n == 6 ? 1000000UL : \
+ n == 7 ? 10000000UL : \
+ n == 8 ? 100000000UL : \
+ 1000000000UL \
+)
+
+static unsigned int cpumask_worst_size(unsigned int nr_bits)
+{
+ /*
+ * Printing all the CPUs separated by a comma is a decent bound for the
+ * maximum memory required to print a cpumask (a slightly better bound
+ * is chunks of 2 bits set, i.e. 0-1,3-4,6-7...).
+ *
+ * e.g. for nr_bits=132:
+ * - 131 commas
+ * - 10 * 1 chars for CPUS [0, 9]
+ * - 90 * 2 chars for CPUS [10-99]
+ * - 32 * 3 chars for CPUS [100-131]
+ */
+ unsigned int last_cpu = nr_bits - 1;
+ unsigned int nr_chars = nr_bits - 1;
+ int last_lvl = log10(last_cpu);
+
+ /* All log10 levels before the last one have all values used */
+ for (int lvl = 0; lvl < last_lvl; lvl++) {
+ int nr_values = ilog10(lvl + 1) - ilog10(lvl);
+
+ nr_chars += nr_values * (lvl + 1);
+ }
+ /* Last level is incomplete */
+ nr_chars += (nr_bits - ilog10(last_lvl)) * (last_lvl + 1);
+
+ return nr_chars;
+}
+
+static void print_cpumask_to_seq(struct tep_handle *tep,
+ struct trace_seq *s, const char *format,
+ int len_arg, const void *data, int size)
+{
+ int firstone = -1, firstzero = -1;
+ int nr_bits = size * 8;
+ bool first = true;
+ int str_size = 0;
+ char buf[12]; /* '-' + log10(2^32) + 1 digits + '\0' */
+ char *str;
+ int index;
+ int i;
+
+ str = malloc(cpumask_worst_size(nr_bits) + 1);
+ if (!str) {
+ do_warning("%s: not enough memory!", __func__);
+ return;
+ }
+
+ for (i = 0; i < size; i++) {
+ unsigned char byte;
+ int fmtsize;
+
+ if (tep->file_bigendian)
+ index = size - (i + 1);
+ else
+ index = i;
+
+ /* Byte by byte scan, not the best... */
+ byte = *(((unsigned char *)data) + index);
+more:
+ /* First find a bit set to one...*/
+ if (firstone < 0 && byte) {
+ /*
+ * Set all lower bits, so a later ffz on this same byte
+ * is guaranteed to find a later bit.
+ */
+ firstone = ffs(byte) - 1;
+ byte |= (1 << firstone) - 1;
+ firstone += i * 8;
+ }
+
+ if (firstone < 0)
+ continue;
+
+ /* ...Then find a bit set to zero */
+ if ((~byte) & 0xFF) {
+ /*
+ * Clear all lower bits, so a later ffs on this same
+ * byte is guaranteed to find a later bit.
+ */
+ firstzero = ffs(~byte) - 1;
+ byte &= ~((1 << (firstzero)) - 1);
+ firstzero += i * 8;
+ } else if (i == size - 1) { /* ...Or reach the end of the mask */
+ firstzero = nr_bits;
+ byte = 0;
+ } else {
+ continue;
+ }
+
+ /* We've found a bit set to one, and a later bit set to zero. */
+ if (!first) {
+ str[str_size] = ',';
+ str_size++;
+ }
+ first = false;
+
+ /* It takes {log10(number) + 1} chars to format a number */
+ fmtsize = log10(firstone) + 1;
+ snprintf(buf, fmtsize + 1, "%d", firstone);
+ memcpy(str + str_size, buf, fmtsize);
+ str_size += fmtsize;
+
+ if (firstzero > firstone + 1) {
+ fmtsize = log10(firstzero - 1) + 2;
+ snprintf(buf, fmtsize + 1, "-%d", firstzero - 1);
+ memcpy(str + str_size, buf, fmtsize);
+ str_size += fmtsize;
+ }
+
+ firstzero = firstone = -1;
+ if (byte)
+ goto more;
+ }
+
+ str[str_size] = 0;
+ str_size++;
+
+ if (len_arg >= 0)
+ trace_seq_printf(s, format, len_arg, str);
+ else
+ trace_seq_printf(s, format, str);
+
+ free(str);
+}
+
static void print_str_arg(struct trace_seq *s, void *data, int size,
struct tep_event *event, const char *format,
int len_arg, struct tep_print_arg *arg)
@@ -4694,7 +4849,6 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
case TEP_PRINT_BSTRING:
print_str_to_seq(s, format, len_arg, arg->string.string);
break;
- case TEP_PRINT_CPUMASK:
case TEP_PRINT_BITMASK: {
if (!arg->bitmask.field) {
arg->bitmask.field = tep_find_any_field(event, arg->bitmask.bitmask);
@@ -4707,6 +4861,18 @@ static void print_str_arg(struct trace_seq *s, void *data, int size,
data + offset, len);
break;
}
+ case TEP_PRINT_CPUMASK: {
+ if (!arg->bitmask.field) {
+ arg->bitmask.field = tep_find_any_field(event, arg->bitmask.bitmask);
+ arg->bitmask.offset = arg->bitmask.field->offset;
+ }
+ if (!arg->bitmask.field)
+ break;
+ dynamic_offset_field(tep, arg->bitmask.field, data, size, &offset, &len);
+ print_cpumask_to_seq(tep, s, format, len_arg,
+ data + offset, len);
+ break;
+ }
case TEP_PRINT_OP:
/*
* The only op for string should be ? :
--
2.31.1
|