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Output: Stream output when printing maps
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Symbolicating user stack traces can be slow for large binaries and when
symbol caching is not effective. When printing a large map containing
stack traces, bpftrace can appear to "hang" while it's stuck
symbolicating all of them, before it prints them in a single batch.

This commit changes the behaviour so that we print each stack trace as
soon as it's ready, to show some progress to the user.
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@ajor
ajor committed Jun 25, 2024
1 parent 65a08f4 commit e942bf2
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Showing 3 changed files with 63 additions and 62 deletions.
2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -10,6 +10,8 @@ and this project adheres to

#### Added
#### Changed
- Stream output when printing maps
- [#3264](https://github.com/bpftrace/bpftrace/pull/3264)
#### Deprecated
#### Removed
#### Fixed
Expand Down
86 changes: 46 additions & 40 deletions src/output.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -382,18 +382,19 @@ std::string Output::struct_to_str(const std::vector<std::string> &elems) const
return "{ " + str_join(elems, ", ") + " }";
}

std::string Output::map_to_str(
void Output::map_contents(
BPFtrace &bpftrace,
const BpfMap &map,
uint32_t top,
uint32_t div,
const std::vector<std::pair<std::vector<uint8_t>, std::vector<uint8_t>>>
&values_by_key) const
{
std::vector<std::string> elems;
uint32_t i = 0;
size_t total = values_by_key.size();
const auto &map_type = bpftrace.resources.maps_info.at(map.name()).value_type;

bool first = true;
for (auto &pair : values_by_key) {
auto key = pair.first;
auto value = pair.second;
Expand All @@ -403,16 +404,19 @@ std::string Output::map_to_str(
continue;
}

if (first)
first = false;
else
map_elem_delim(map_type);

auto key_str = map_key_to_str(bpftrace, map, key);
auto value_str = value_to_str(
bpftrace, map_type, value, map.is_per_cpu_type(), div);
elems.push_back(map_keyval_to_str(map_type, key_str, value_str));
map_key_val(map_type, key_str, value_str);
}

return str_join(elems, map_elem_delim_to_str(map_type));
}

std::string Output::map_hist_to_str(
void Output::map_hist_contents(
BPFtrace &bpftrace,
const BpfMap &map,
uint32_t top,
Expand All @@ -421,17 +425,22 @@ std::string Output::map_hist_to_str(
const std::vector<std::pair<std::vector<uint8_t>, uint64_t>>
&total_counts_by_key) const
{
std::vector<std::string> elems;
uint32_t i = 0;
const auto &map_info = bpftrace.resources.maps_info.at(map.name());
const auto &map_type = map_info.value_type;
bool first = true;
for (auto &key_count : total_counts_by_key) {
auto &key = key_count.first;
auto &value = values_by_key.at(key);

if (top && values_by_key.size() > top && i++ < (values_by_key.size() - top))
continue;

if (first)
first = false;
else
map_elem_delim(map_type);

auto key_str = map_key_to_str(bpftrace, map, key);
std::string val_str;
if (map_type.IsHistTy()) {
Expand All @@ -440,13 +449,11 @@ std::string Output::map_hist_to_str(
auto &args = map_info.lhist_args;
val_str = lhist_to_str(value, args->min, args->max, args->step);
}

elems.push_back(map_keyval_to_str(map_type, key_str, val_str));
map_key_val(map_type, key_str, val_str);
}
return str_join(elems, map_elem_delim_to_str(map_type));
}

std::string Output::map_stats_to_str(
void Output::map_stats_contents(
BPFtrace &bpftrace,
const BpfMap &map,
uint32_t top,
Expand All @@ -455,9 +462,9 @@ std::string Output::map_stats_to_str(
const std::vector<std::pair<std::vector<uint8_t>, int64_t>>
&total_counts_by_key) const
{
std::vector<std::string> elems;
const auto &map_type = bpftrace.resources.maps_info.at(map.name()).value_type;
uint32_t i = 0;
bool first = true;
for (auto &key_count : total_counts_by_key) {
auto &key = key_count.first;
auto &value = values_by_key.at(key);
Expand All @@ -466,6 +473,11 @@ std::string Output::map_stats_to_str(
i++ < (values_by_key.size() - top))
continue;

if (first)
first = false;
else
map_elem_delim(map_type);

auto key_str = map_key_to_str(bpftrace, map, key);

int64_t count = (int64_t)value.at(0);
Expand All @@ -484,10 +496,8 @@ std::string Output::map_stats_to_str(
} else
value_str = std::to_string(average / div);

elems.push_back(map_keyval_to_str(map_type, key_str, value_str));
map_key_val(map_type, key_str, value_str);
}

return str_join(elems, map_elem_delim_to_str(map_type));
}

void TextOutput::map(
Expand All @@ -498,7 +508,7 @@ void TextOutput::map(
const std::vector<std::pair<std::vector<uint8_t>, std::vector<uint8_t>>>
&values_by_key) const
{
out_ << map_to_str(bpftrace, map, top, div, values_by_key);
map_contents(bpftrace, map, top, div, values_by_key);
out_ << std::endl;
}

Expand Down Expand Up @@ -599,7 +609,7 @@ void TextOutput::map_hist(
const std::vector<std::pair<std::vector<uint8_t>, uint64_t>>
&total_counts_by_key) const
{
out_ << map_hist_to_str(
map_hist_contents(
bpftrace, map, top, div, values_by_key, total_counts_by_key);
out_ << std::endl;
}
Expand All @@ -613,7 +623,7 @@ void TextOutput::map_stats(
const std::vector<std::pair<std::vector<uint8_t>, int64_t>>
&total_counts_by_key) const
{
out_ << map_stats_to_str(
map_stats_contents(
bpftrace, map, top, div, values_by_key, total_counts_by_key);
out_ << std::endl << std::endl;
}
Expand Down Expand Up @@ -677,24 +687,21 @@ std::string TextOutput::map_key_to_str(BPFtrace &bpftrace,
return map.name() + map_key.argument_value_list_str(bpftrace, key);
}

std::string TextOutput::map_keyval_to_str(const SizedType &map_type,
const std::string &key,
const std::string &val) const
void TextOutput::map_key_val(const SizedType &map_type,
const std::string &key,
const std::string &val) const
{
std::string res = key + ": ";
out_ << key + ": ";
if (map_type.IsHistTy() || map_type.IsLhistTy())
res += "\n";
res += val;
return res;
out_ << "\n";
out_ << val;
}

std::string TextOutput::map_elem_delim_to_str(const SizedType &map_type) const
void TextOutput::map_elem_delim(const SizedType &map_type) const
{
if (!map_type.IsKstackTy() && !map_type.IsUstackTy() &&
!map_type.IsKsymTy() && !map_type.IsUsymTy() && !map_type.IsInetTy())
return "\n";

return "";
out_ << "\n";
}

std::string TextOutput::key_value_pairs_to_str(
Expand Down Expand Up @@ -762,7 +769,7 @@ void JsonOutput::map(
if (map_key.size() > 0) // check if this map has keys
out_ << "{";

out_ << map_to_str(bpftrace, map, top, div, values_by_key);
map_contents(bpftrace, map, top, div, values_by_key);

if (map_key.size() > 0)
out_ << "}";
Expand Down Expand Up @@ -872,7 +879,7 @@ void JsonOutput::map_hist(
if (map_key.size() > 0) // check if this map has keys
out_ << "{";

out_ << map_hist_to_str(
map_hist_contents(
bpftrace, map, top, div, values_by_key, total_counts_by_key);

if (map_key.size() > 0)
Expand All @@ -899,7 +906,7 @@ void JsonOutput::map_stats(
if (map_key.size() > 0) // check if this map has keys
out_ << "{";

out_ << map_stats_to_str(
map_stats_contents(
bpftrace, map, top, div, values_by_key, total_counts_by_key);

if (map_key.size() > 0)
Expand Down Expand Up @@ -991,18 +998,17 @@ std::string JsonOutput::map_key_to_str(BPFtrace &bpftrace,
return "";
}

std::string JsonOutput::map_keyval_to_str(const SizedType &map_type
__attribute__((unused)),
const std::string &key,
const std::string &val) const
void JsonOutput::map_key_val(const SizedType &map_type __attribute__((unused)),
const std::string &key,
const std::string &val) const
{
return key.empty() ? val : key + ": " + val;
out_ << (key.empty() ? val : key + ": " + val);
}

std::string JsonOutput::map_elem_delim_to_str(const SizedType &map
__attribute__((unused))) const
void JsonOutput::map_elem_delim(const SizedType &map
__attribute__((unused))) const
{
return ", ";
out_ << ", ";
}

std::string JsonOutput::key_value_pairs_to_str(
Expand Down
37 changes: 15 additions & 22 deletions src/output.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -53,8 +53,6 @@ class Output {
};

// Write map to output
// Ideally, the implementation should use map_to_str to convert a map into
// a string, format it properly, and print it to out_.
virtual void map(
BPFtrace &bpftrace,
const BpfMap &map,
Expand All @@ -63,8 +61,6 @@ class Output {
const std::vector<std::pair<std::vector<uint8_t>, std::vector<uint8_t>>>
&values_by_key) const = 0;
// Write map histogram to output
// Ideally, the implementation should use map_hist_to_str to convert a map
// histogram into a string, format it properly, and print it to out_.
virtual void map_hist(
BPFtrace &bpftrace,
const BpfMap &map,
Expand All @@ -75,8 +71,6 @@ class Output {
const std::vector<std::pair<std::vector<uint8_t>, uint64_t>>
&total_counts_by_key) const = 0;
// Write map statistics to output
// Ideally, the implementation should use map_stats_to_str to convert map
// statistics into a string, format it properly, and print it to out_.
virtual void map_stats(
BPFtrace &bpftrace,
const BpfMap &map,
Expand Down Expand Up @@ -131,7 +125,7 @@ class Output {
// Convert map into string
// Default behaviour: format each (key, value) pair using output-specific
// methods and join them into a single string
virtual std::string map_to_str(
virtual void map_contents(
BPFtrace &bpftrace,
const BpfMap &map,
uint32_t top,
Expand All @@ -141,7 +135,7 @@ class Output {
// Convert map histogram into string
// Default behaviour: format each (key, hist) pair using output-specific
// methods and join them into a single string
virtual std::string map_hist_to_str(
virtual void map_hist_contents(
BPFtrace &bpftrace,
const BpfMap &map,
uint32_t top,
Expand All @@ -153,7 +147,7 @@ class Output {
// Convert map statistics into string
// Default behaviour: format each (key, stats) pair using output-specific
// methods and join them into a single string
virtual std::string map_stats_to_str(
virtual void map_stats_contents(
BPFtrace &bpftrace,
const BpfMap &map,
uint32_t top,
Expand All @@ -166,12 +160,11 @@ class Output {
const BpfMap &map,
const std::vector<uint8_t> &key) const = 0;
// Properly join map key and value strings
virtual std::string map_keyval_to_str(const SizedType &map_type,
const std::string &key,
const std::string &val) const = 0;
virtual void map_key_val(const SizedType &map_type,
const std::string &key,
const std::string &val) const = 0;
// Delimiter to join (properly formatted) map elements into a single string
virtual std::string map_elem_delim_to_str(
const SizedType &map_type) const = 0;
virtual void map_elem_delim(const SizedType &map_type) const = 0;
// Convert non-map value into string
// This method should properly handle all non-map value types.
// Aggregate types (array, struct, tuple) are formatted using output-specific
Expand Down Expand Up @@ -261,10 +254,10 @@ class TextOutput : public Output {
std::string map_key_to_str(BPFtrace &bpftrace,
const BpfMap &map,
const std::vector<uint8_t> &key) const override;
std::string map_keyval_to_str(const SizedType &map_type,
const std::string &key,
const std::string &val) const override;
std::string map_elem_delim_to_str(const SizedType &map_type) const override;
void map_key_val(const SizedType &map_type,
const std::string &key,
const std::string &val) const override;
void map_elem_delim(const SizedType &map_type) const override;
std::string field_to_str(const std::string &name,
const std::string &value) const override;
std::string tuple_to_str(
Expand Down Expand Up @@ -340,10 +333,10 @@ class JsonOutput : public Output {
std::string map_key_to_str(BPFtrace &bpftrace,
const BpfMap &map,
const std::vector<uint8_t> &key) const override;
std::string map_keyval_to_str(const SizedType &map_type,
const std::string &key,
const std::string &val) const override;
std::string map_elem_delim_to_str(const SizedType &map_type) const override;
void map_key_val(const SizedType &map_type,
const std::string &key,
const std::string &val) const override;
void map_elem_delim(const SizedType &map_type) const override;
std::string field_to_str(const std::string &name,
const std::string &value) const override;
std::string tuple_to_str(
Expand Down

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