ircd::prof: Add interface to pressure stall information on linux platforms.

include/ircd/prof/prof.h

@@ -41,6 +41,7 @@ namespace ircd::prof
 #include "resource.h"
 #include "times.h"
 #include "system.h"
+#include "psi.h"
 
 // Exports to ircd::
 namespace ircd

include/ircd/prof/psi.h

@@ -0,0 +1,52 @@
+// Matrix Construct
+//
+// Copyright (C) Matrix Construct Developers, Authors & Contributors
+// Copyright (C) 2016-2019 Jason Volk <jason@zemos.net>
+//
+// Permission to use, copy, modify, and/or distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice is present in all copies. The
+// full license for this software is available in the LICENSE file.
+
+#pragma once
+#define HAVE_IRCD_PROF_PSI_H
+
+namespace ircd::prof::psi
+{
+	struct file;
+	struct metric;
+	struct refresh;
+
+	bool refresh(file &) noexcept;
+
+	extern const bool supported;
+	extern file cpu, mem, io;
+}
+
+struct ircd::prof::psi::metric
+{
+	struct avg
+	{
+		seconds window;
+		float pct;
+	};
+
+	std::array<struct avg, 3> avg;
+	microseconds stall;
+};
+
+struct ircd::prof::psi::file
+{
+	string_view name;
+	system_point sampled;
+	metric some, full;
+};
+
+#ifndef __linux__
+inline bool
+ircd::prof::psi::refresh(metric &)
+noexcept
+{
+	return false; // unsupported platform
+}
+#endif

ircd/prof_linux.cc

@@ -154,6 +154,131 @@ catch(const std::exception &e)
 	return nullptr;
 }
 
+///////////////////////////////////////////////////////////////////////////////
+//
+// prof/psi.h
+//
+
+decltype(ircd::prof::psi::supported)
+ircd::prof::psi::supported
+{
+	info::kernel_version[0] > 4 ||
+	(info::kernel_version[0] >= 4 && info::kernel_version[1] >= 20)
+};
+
+decltype(ircd::prof::psi::cpu)
+ircd::prof::psi::cpu
+{
+	"cpu"
+};
+
+decltype(ircd::prof::psi::mem)
+ircd::prof::psi::mem
+{
+	"memory"
+};
+
+decltype(ircd::prof::psi::io)
+ircd::prof::psi::io
+{
+	"io"
+};
+
+//
+// prof::psi::metric::refresh
+//
+
+bool
+ircd::prof::psi::refresh(file &file)
+noexcept try
+{
+	if(!supported)
+		return false;
+
+	if(unlikely(!file.name))
+		return false;
+
+	thread_local unique_mutable_buffer path_buf
+	{
+		fs::PATH_MAX_LEN
+	};
+
+	const auto &path
+	{
+		fs::path(path_buf, vector_view<const string_view>
+		{
+			"/proc/pressure"_sv, file.name
+		})
+	};
+
+	// Copy value into userspace
+	char buf[256];
+	fs::read_opts opts;
+	opts.aio = false; // can't read /proc through AIO
+	opts.all = false; // don't need posix read-loop; make one read(2) only.
+	const auto &result
+	{
+		fs::read(path, buf, opts)
+	};
+
+	tokens(result, '\n', [&file] // Read each line
+	(const string_view &line)
+	{
+		const auto &[type, vals]
+		{
+			split(line, ' ')
+		};
+
+		// The first token tells us what the metric is; we have allocated
+		// results for the following
+		if(type != "full" && type != "some")
+			return;
+
+		auto &metric
+		{
+			type == "full"?
+				file.full:
+				file.some
+		};
+
+		size_t i(0);
+		tokens(vals, ' ', [&metric, &i] // Read each key=value pair
+		(const string_view &key_val)
+		{
+			const auto &[key, val]
+			{
+				split(key_val, '=')
+			};
+
+			if(key == "total")
+			{
+				metric.stall = lex_cast<microseconds>(val);
+				return;
+			}
+			else if(startswith(key, "avg") && i < metric.avg.size())
+			{
+				metric.avg.at(i).window = lex_cast<seconds>(lstrip(key, "avg"));
+				metric.avg.at(i).pct = lex_cast<float>(val);
+				++i;
+			}
+		});
+	});
+
+	file.sampled = ircd::now<system_point>();
+	return true;
+}
+catch(const std::exception &e)
+{
+	log::error
+	{
+		"Failed to refresh pressure stall information '%s' :%s",
+		file.name,
+		e.what(),
+	};
+
+	return false;
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 //
 // prof/instructions.h

modules/console.cc

@@ -1194,6 +1194,64 @@ console_cmd__vg(opt &out, const string_view &line)
 // prof
 //
 
+bool
+console_cmd__prof__psi(opt &out, const string_view &line)
+{
+	const auto show_file{[&out]
+	(const string_view &name, prof::psi::file &file)
+	{
+		if(!refresh(file))
+			return;
+
+		char pbuf[48];
+		out
+		<< std::left << name
+		<< " some stall    "
+		<< pretty(pbuf, file.some.stall)
+		<< " ("
+		<< file.some.stall.count()
+		<< ')'
+		<< std::endl
+		;
+		for(size_t i(0); i < file.some.avg.size(); i++)
+			out
+			<< std::left << name
+			<< " some  "
+			<< std::right << std::setw(3) << file.some.avg.at(i).window.count()
+			<< "s        "
+			<< std::right << std::setw(4) << file.some.avg.at(i).pct << '%'
+			<< std::endl
+			;
+
+		out
+		<< std::endl
+		<< std::left << name
+		<< " full stall    "
+		<< pretty(pbuf, file.full.stall)
+		<< " ("
+		<< file.full.stall.count()
+		<< ')'
+		<< std::endl
+		;
+		for(size_t i(0); i < file.full.avg.size(); i++)
+			out
+			<< std::left << name
+			<< " full  "
+			<< std::right << std::setw(3) << file.full.avg.at(i).window.count()
+			<< "s        "
+			<< std::right << std::setw(4) << file.full.avg.at(i).pct << '%'
+			<< std::endl
+			;
+
+		out << std::endl;
+	}};
+
+	show_file("cpu", prof::psi::cpu);
+	show_file("mem", prof::psi::mem);
+	show_file("io ", prof::psi::io);
+	return true;
+}
+
 bool
 console_cmd__prof__vg__start(opt &out, const string_view &line)
 {