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LibCore: Allow caching and reusing the ProcFS file descriptors

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Because ProcFS will refresh the data upon seek to 0, we can re-use
the same file descriptor. This saves us from having to open it every
time, but it also reduces the odds that we are unable to open a new
file descriptor due to low memory conditions.
This commit is contained in:
Tom 2021-01-03 10:08:51 -07:00 committed by Andreas Kling
parent cf89180c35
commit bc3c0fa936
Notes: sideshowbarker 2024-07-19 00:08:28 +09:00 
Author: https://github.com/tomuta
Commit: https://github.com/SerenityOS/serenity/commit/bc3c0fa9362
Pull-request: https://github.com/SerenityOS/serenity/pull/4736
2 changed files with 21 additions and 6 deletions
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25
Libraries/LibCore/ProcessStatisticsReader.cpp
View file

@ -37,17 +37,24 @@ namespace Core {
HashMap<uid_t, String> ProcessStatisticsReader::s_usernames;
Optional<HashMap<pid_t, Core::ProcessStatistics>> ProcessStatisticsReader::get_all()
Optional<HashMap<pid_t, Core::ProcessStatistics>> ProcessStatisticsReader::get_all(RefPtr<Core::File>& proc_all_file)
{
auto file = Core::File::construct("/proc/all");
if (!file->open(Core::IODevice::ReadOnly)) {
fprintf(stderr, "ProcessStatisticsReader: Failed to open /proc/all: %s\n", file->error_string());
return {};
if (proc_all_file) {
if (!proc_all_file->seek(0, Core::File::SeekMode::SetPosition)) {
fprintf(stderr, "ProcessStatisticsReader: Failed to refresh /proc/all: %s\n", proc_all_file->error_string());
return {};
}
} else {
proc_all_file = Core::File::construct("/proc/all");
if (!proc_all_file->open(Core::IODevice::ReadOnly)) {
fprintf(stderr, "ProcessStatisticsReader: Failed to open /proc/all: %s\n", proc_all_file->error_string());
return {};
}
}
HashMap<pid_t, Core::ProcessStatistics> map;
auto file_contents = file->read_all();
auto file_contents = proc_all_file->read_all();
auto json = JsonValue::from_string(file_contents);
if (!json.has_value())
return {};
@ -112,6 +119,12 @@ Optional<HashMap<pid_t, Core::ProcessStatistics>> ProcessStatisticsReader::get_a
return map;
}
Optional<HashMap<pid_t, Core::ProcessStatistics>> ProcessStatisticsReader::get_all()
{
RefPtr<Core::File> proc_all_file;
return get_all(proc_all_file);
}
String ProcessStatisticsReader::username_from_uid(uid_t uid)
{
if (s_usernames.is_empty()) {

2
Libraries/LibCore/ProcessStatisticsReader.h
View file

@ -28,6 +28,7 @@
#include <AK/HashMap.h>
#include <AK/String.h>
#include <LibCore/File.h>
#include <unistd.h>
namespace Core {
@ -86,6 +87,7 @@ struct ProcessStatistics {
class ProcessStatisticsReader {
public:
static Optional<HashMap<pid_t, Core::ProcessStatistics>> get_all(RefPtr<Core::File>&);
static Optional<HashMap<pid_t, Core::ProcessStatistics>> get_all();
private: