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Kernel+LibCore: Make %sid path parsing not take ages
Before this patch, Core::SessionManagement::parse_path_with_sid() would figure out the root session ID by sifting through /sys/kernel/processes. That file can take quite a while to generate (sometimes up to 40ms on my machine, which is a problem on its own!) and with no caching, many of our programs were effectively doing this multiple times on startup when unveiling something in /tmp/session/%sid/ While we should find ways to make generating /sys/kernel/processes fast again, this patch addresses the specific problem by introducing a new syscall: sys$get_root_session_id(). This extracts the root session ID by looking directly at the process table and takes <1ms instead of 40ms. This cuts WebContent process startup time by ~100ms on my machine. :^)
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4 changed files with 36 additions and 24 deletions
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@ -5,37 +5,26 @@
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*/
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#include <LibCore/Directory.h>
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#include <LibCore/ProcessStatisticsReader.h>
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#include <LibCore/SessionManagement.h>
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#include <LibCore/System.h>
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#ifdef AK_OS_SERENITY
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# include <LibSystem/syscall.h>
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#endif
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namespace Core::SessionManagement {
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static ErrorOr<Core::ProcessStatistics const*> get_proc(Core::AllProcessesStatistics const& stats, pid_t pid)
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ErrorOr<pid_t> root_session_id([[maybe_unused]] Optional<pid_t> force_sid)
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{
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for (auto& proc : stats.processes) {
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if (proc.pid == pid)
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return &proc;
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#ifdef AK_OS_SERENITY
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int rc = syscall(SC_get_root_session_id, force_sid.value_or(-1));
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if (rc < 0) {
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return Error::from_syscall("get_root_session_id"sv, rc);
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}
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return Error::from_string_literal("Could not find pid in process statistics.");
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}
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ErrorOr<pid_t> root_session_id(Optional<pid_t> force_sid)
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{
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auto stats = TRY(Core::ProcessStatisticsReader::get_all(false));
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pid_t sid = (force_sid.has_value()) ? force_sid.value() : TRY(System::getsid());
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while (true) {
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pid_t parent = TRY(get_proc(stats, sid))->ppid;
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pid_t parent_sid = TRY(get_proc(stats, parent))->sid;
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if (parent_sid == 0)
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break;
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sid = parent_sid;
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}
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return sid;
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return static_cast<pid_t>(rc);
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#else
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return 0;
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#endif
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}
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ErrorOr<void> logout(Optional<pid_t> force_sid)
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