kmemtrace: Core implementation.

kmemtrace provides tracing for slab allocator functions, such as kmalloc,
kfree, kmem_cache_alloc, kmem_cache_free etc.. Collected data is then fed
to the userspace application in order to analyse allocation hotspots,
internal fragmentation and so on, making it possible to see how well an
allocator performs, as well as debug and profile kernel code.
Signed-off-by: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Signed-off-by: Pekka Enberg <penberg@cs.helsinki.fi>

Documentation/kernel-parameters.txt

@@ -49,6 +49,7 @@ parameter is applicable:
 	ISAPNP	ISA PnP code is enabled.
 	ISDN	Appropriate ISDN support is enabled.
 	JOY	Appropriate joystick support is enabled.
+	KMEMTRACE kmemtrace is enabled.
 	LIBATA  Libata driver is enabled
 	LP	Printer support is enabled.
 	LOOP	Loopback device support is enabled.
@@ -1018,6 +1019,15 @@ and is between 256 and 4096 characters. It is defined in the file
 			use the HighMem zone if it exists, and the Normal
 			zone if it does not.
 
+	kmemtrace.enable=	[KNL,KMEMTRACE] Format: { yes | no }
+				Controls whether kmemtrace is enabled
+				at boot-time.
+
+	kmemtrace.subbufs=n	[KNL,KMEMTRACE] Overrides the number of
+			subbufs kmemtrace's relay channel has. Set this
+			higher than default (KMEMTRACE_N_SUBBUFS in code) if
+			you experience buffer overruns.
+
 	movablecore=nn[KMG]	[KNL,X86-32,IA-64,PPC,X86-64] This parameter
 			is similar to kernelcore except it specifies the
 			amount of memory used for migratable allocations.

MAINTAINERS

@@ -2565,6 +2565,12 @@ M:	jason.wessel@windriver.com
 L:	kgdb-bugreport@lists.sourceforge.net
 S:	Maintained
 
+KMEMTRACE
+P:	Eduard - Gabriel Munteanu
+M:	eduard.munteanu@linux360.ro
+L:	linux-kernel@vger.kernel.org
+S:	Maintained
+
 KPROBES
 P:	Ananth N Mavinakayanahalli
 M:	ananth@in.ibm.com

include/linux/kmemtrace.h

+/*
+ * Copyright (C) 2008 Eduard - Gabriel Munteanu
+ *
+ * This file is released under GPL version 2.
+ */
+
+#ifndef _LINUX_KMEMTRACE_H
+#define _LINUX_KMEMTRACE_H
+
+#ifdef __KERNEL__
+
+#include <linux/types.h>
+#include <linux/marker.h>
+
+enum kmemtrace_type_id {
+	KMEMTRACE_TYPE_KMALLOC = 0,	/* kmalloc() or kfree(). */
+	KMEMTRACE_TYPE_CACHE,		/* kmem_cache_*(). */
+	KMEMTRACE_TYPE_PAGES,		/* __get_free_pages() and friends. */
+};
+
+#ifdef CONFIG_KMEMTRACE
+
+extern void kmemtrace_init(void);
+
+static inline void kmemtrace_mark_alloc_node(enum kmemtrace_type_id type_id,
+					     unsigned long call_site,
+					     const void *ptr,
+					     size_t bytes_req,
+					     size_t bytes_alloc,
+					     gfp_t gfp_flags,
+					     int node)
+{
+	trace_mark(kmemtrace_alloc, "type_id %d call_site %lu ptr %lu "
+		   "bytes_req %lu bytes_alloc %lu gfp_flags %lu node %d",
+		   type_id, call_site, (unsigned long) ptr,
+		   bytes_req, bytes_alloc, (unsigned long) gfp_flags, node);
+}
+
+static inline void kmemtrace_mark_free(enum kmemtrace_type_id type_id,
+				       unsigned long call_site,
+				       const void *ptr)
+{
+	trace_mark(kmemtrace_free, "type_id %d call_site %lu ptr %lu",
+		   type_id, call_site, (unsigned long) ptr);
+}
+
+#else /* CONFIG_KMEMTRACE */
+
+static inline void kmemtrace_init(void)
+{
+}
+
+static inline void kmemtrace_mark_alloc_node(enum kmemtrace_type_id type_id,
+					     unsigned long call_site,
+					     const void *ptr,
+					     size_t bytes_req,
+					     size_t bytes_alloc,
+					     gfp_t gfp_flags,
+					     int node)
+{
+}
+
+static inline void kmemtrace_mark_free(enum kmemtrace_type_id type_id,
+				       unsigned long call_site,
+				       const void *ptr)
+{
+}
+
+#endif /* CONFIG_KMEMTRACE */
+
+static inline void kmemtrace_mark_alloc(enum kmemtrace_type_id type_id,
+					unsigned long call_site,
+					const void *ptr,
+					size_t bytes_req,
+					size_t bytes_alloc,
+					gfp_t gfp_flags)
+{
+	kmemtrace_mark_alloc_node(type_id, call_site, ptr,
+				  bytes_req, bytes_alloc, gfp_flags, -1);
+}
+
+#endif /* __KERNEL__ */
+
+#endif /* _LINUX_KMEMTRACE_H */
+

init/main.c

@@ -69,6 +69,7 @@
 #include <asm/setup.h>
 #include <asm/sections.h>
 #include <asm/cacheflush.h>
+#include <linux/kmemtrace.h>
 
 #ifdef CONFIG_X86_LOCAL_APIC
 #include <asm/smp.h>
@@ -653,6 +654,7 @@ asmlinkage void __init start_kernel(void)
 	enable_debug_pagealloc();
 	cpu_hotplug_init();
 	kmem_cache_init();
+	kmemtrace_init();
 	debug_objects_mem_init();
 	idr_init_cache();
 	setup_per_cpu_pageset();

lib/Kconfig.debug

@@ -803,6 +803,34 @@ config FIREWIRE_OHCI_REMOTE_DMA
 
 	  If unsure, say N.
 
+config KMEMTRACE
+	bool "Kernel memory tracer (kmemtrace)"
+	depends on RELAY && DEBUG_FS && MARKERS
+	help
+	  kmemtrace provides tracing for slab allocator functions, such as
+	  kmalloc, kfree, kmem_cache_alloc, kmem_cache_free etc.. Collected
+	  data is then fed to the userspace application in order to analyse
+	  allocation hotspots, internal fragmentation and so on, making it
+	  possible to see how well an allocator performs, as well as debug
+	  and profile kernel code.
+
+	  This requires an userspace application to use. See
+	  Documentation/vm/kmemtrace.txt for more information.
+
+	  Saying Y will make the kernel somewhat larger and slower. However,
+	  if you disable kmemtrace at run-time or boot-time, the performance
+	  impact is minimal (depending on the arch the kernel is built for).
+
+	  If unsure, say N.
+
+config KMEMTRACE_DEFAULT_ENABLED
+	bool "Enabled by default at boot"
+	depends on KMEMTRACE
+	help
+	  Say Y here to enable kmemtrace at boot-time by default. Whatever
+	  the choice, the behavior can be overridden by a kernel parameter,
+	  as described in documentation.
+
 menuconfig BUILD_DOCSRC
 	bool "Build targets in Documentation/ tree"
 	depends on HEADERS_CHECK

mm/Makefile

@@ -34,3 +34,4 @@ obj-$(CONFIG_MIGRATION) += migrate.o
 obj-$(CONFIG_SMP) += allocpercpu.o
 obj-$(CONFIG_QUICKLIST) += quicklist.o
 obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
+obj-$(CONFIG_KMEMTRACE) += kmemtrace.o

mm/kmemtrace.c

+/*
+ * Copyright (C) 2008 Pekka Enberg, Eduard - Gabriel Munteanu
+ *
+ * This file is released under GPL version 2.
+ */
+
+#include <linux/string.h>
+#include <linux/debugfs.h>
+#include <linux/relay.h>
+#include <linux/module.h>
+#include <linux/marker.h>
+#include <linux/gfp.h>
+#include <linux/kmemtrace.h>
+
+#define KMEMTRACE_SUBBUF_SIZE		524288
+#define KMEMTRACE_DEF_N_SUBBUFS		20
+
+static struct rchan *kmemtrace_chan;
+static u32 kmemtrace_buf_overruns;
+
+static unsigned int kmemtrace_n_subbufs;
+#ifdef CONFIG_KMEMTRACE_DEFAULT_ENABLED
+static unsigned int kmemtrace_enabled = 1;
+#else
+static unsigned int kmemtrace_enabled = 0;
+#endif
+
+/*
+ * The sequence number is used for reordering kmemtrace packets
+ * in userspace, since they are logged as per-CPU data.
+ *
+ * atomic_t should always be a 32-bit signed integer. Wraparound is not
+ * likely to occur, but userspace can deal with it by expecting a certain
+ * sequence number in the next packet that will be read.
+ */
+static atomic_t kmemtrace_seq_num;
+
+#define KMEMTRACE_ABI_VERSION		1
+
+static u32 kmemtrace_abi_version __read_mostly = KMEMTRACE_ABI_VERSION;
+
+enum kmemtrace_event_id {
+	KMEMTRACE_EVENT_ALLOC = 0,
+	KMEMTRACE_EVENT_FREE,
+};
+
+struct kmemtrace_event {
+	u8		event_id;
+	u8		type_id;
+	u16		event_size;
+	s32		seq_num;
+	u64		call_site;
+	u64		ptr;
+} __attribute__ ((__packed__));
+
+struct kmemtrace_stats_alloc {
+	u64		bytes_req;
+	u64		bytes_alloc;
+	u32		gfp_flags;
+	s32		numa_node;
+} __attribute__ ((__packed__));
+
+static void kmemtrace_probe_alloc(void *probe_data, void *call_data,
+				  const char *format, va_list *args)
+{
+	unsigned long flags;
+	struct kmemtrace_event *ev;
+	struct kmemtrace_stats_alloc *stats;
+	void *buf;
+
+	local_irq_save(flags);
+
+	buf = relay_reserve(kmemtrace_chan,
+			    sizeof(struct kmemtrace_event) +
+			    sizeof(struct kmemtrace_stats_alloc));
+	if (!buf)
+		goto failed;
+
+	/*
+	 * Don't convert this to use structure initializers,
+	 * C99 does not guarantee the rvalues evaluation order.
+	 */
+
+	ev = buf;
+	ev->event_id = KMEMTRACE_EVENT_ALLOC;
+	ev->type_id = va_arg(*args, int);
+	ev->event_size = sizeof(struct kmemtrace_event) +
+			 sizeof(struct kmemtrace_stats_alloc);
+	ev->seq_num = atomic_add_return(1, &kmemtrace_seq_num);
+	ev->call_site = va_arg(*args, unsigned long);
+	ev->ptr = va_arg(*args, unsigned long);
+
+	stats = buf + sizeof(struct kmemtrace_event);
+	stats->bytes_req = va_arg(*args, unsigned long);
+	stats->bytes_alloc = va_arg(*args, unsigned long);
+	stats->gfp_flags = va_arg(*args, unsigned long);
+	stats->numa_node = va_arg(*args, int);
+
+failed:
+	local_irq_restore(flags);
+}
+
+static void kmemtrace_probe_free(void *probe_data, void *call_data,
+				 const char *format, va_list *args)
+{
+	unsigned long flags;
+	struct kmemtrace_event *ev;
+
+	local_irq_save(flags);
+
+	ev = relay_reserve(kmemtrace_chan, sizeof(struct kmemtrace_event));
+	if (!ev)
+		goto failed;
+
+	/*
+	 * Don't convert this to use structure initializers,
+	 * C99 does not guarantee the rvalues evaluation order.
+	 */
+	ev->event_id = KMEMTRACE_EVENT_FREE;
+	ev->type_id = va_arg(*args, int);
+	ev->event_size = sizeof(struct kmemtrace_event);
+	ev->seq_num = atomic_add_return(1, &kmemtrace_seq_num);
+	ev->call_site = va_arg(*args, unsigned long);
+	ev->ptr = va_arg(*args, unsigned long);
+
+failed:
+	local_irq_restore(flags);
+}
+
+static struct dentry *
+kmemtrace_create_buf_file(const char *filename, struct dentry *parent,
+			  int mode, struct rchan_buf *buf, int *is_global)
+{
+	return debugfs_create_file(filename, mode, parent, buf,
+				   &relay_file_operations);
+}
+
+static int kmemtrace_remove_buf_file(struct dentry *dentry)
+{
+	debugfs_remove(dentry);
+
+	return 0;
+}
+
+static int kmemtrace_subbuf_start(struct rchan_buf *buf,
+				  void *subbuf,
+				  void *prev_subbuf,
+				  size_t prev_padding)
+{
+	if (relay_buf_full(buf)) {
+		/*
+		 * We know it's not SMP-safe, but neither
+		 * debugfs_create_u32() is.
+		 */
+		kmemtrace_buf_overruns++;
+		return 0;
+	}
+
+	return 1;
+}
+
+static struct rchan_callbacks relay_callbacks = {
+	.create_buf_file = kmemtrace_create_buf_file,
+	.remove_buf_file = kmemtrace_remove_buf_file,
+	.subbuf_start = kmemtrace_subbuf_start,
+};
+
+static struct dentry *kmemtrace_dir;
+static struct dentry *kmemtrace_overruns_dentry;
+static struct dentry *kmemtrace_abi_version_dentry;
+
+static struct dentry *kmemtrace_enabled_dentry;
+
+static int kmemtrace_start_probes(void)
+{
+	int err;
+
+	err = marker_probe_register("kmemtrace_alloc", "type_id %d "
+				    "call_site %lu ptr %lu "
+				    "bytes_req %lu bytes_alloc %lu "
+				    "gfp_flags %lu node %d",
+				    kmemtrace_probe_alloc, NULL);
+	if (err)
+		return err;
+	err = marker_probe_register("kmemtrace_free", "type_id %d "
+				    "call_site %lu ptr %lu",
+				    kmemtrace_probe_free, NULL);
+
+	return err;
+}
+
+static void kmemtrace_stop_probes(void)
+{
+	marker_probe_unregister("kmemtrace_alloc",
+				kmemtrace_probe_alloc, NULL);
+	marker_probe_unregister("kmemtrace_free",
+				kmemtrace_probe_free, NULL);
+}
+
+static int kmemtrace_enabled_get(void *data, u64 *val)
+{
+	*val = *((int *) data);
+
+	return 0;
+}
+
+static int kmemtrace_enabled_set(void *data, u64 val)
+{
+	u64 old_val = kmemtrace_enabled;
+
+	*((int *) data) = !!val;
+
+	if (old_val == val)
+		return 0;
+	if (val)
+		kmemtrace_start_probes();
+	else
+		kmemtrace_stop_probes();
+
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(kmemtrace_enabled_fops,
+			kmemtrace_enabled_get,
+			kmemtrace_enabled_set, "%llu\n");
+
+static void kmemtrace_cleanup(void)
+{
+	if (kmemtrace_enabled_dentry)
+		debugfs_remove(kmemtrace_enabled_dentry);
+
+	kmemtrace_stop_probes();
+
+	if (kmemtrace_abi_version_dentry)
+		debugfs_remove(kmemtrace_abi_version_dentry);
+	if (kmemtrace_overruns_dentry)
+		debugfs_remove(kmemtrace_overruns_dentry);
+
+	relay_close(kmemtrace_chan);
+	kmemtrace_chan = NULL;
+
+	if (kmemtrace_dir)
+		debugfs_remove(kmemtrace_dir);
+}
+
+static int __init kmemtrace_setup_late(void)
+{
+	if (!kmemtrace_chan)
+		goto failed;
+
+	kmemtrace_dir = debugfs_create_dir("kmemtrace", NULL);
+	if (!kmemtrace_dir)
+		goto cleanup;
+
+	kmemtrace_abi_version_dentry =
+		debugfs_create_u32("abi_version", S_IRUSR,
+				   kmemtrace_dir, &kmemtrace_abi_version);
+	kmemtrace_overruns_dentry =
+		debugfs_create_u32("total_overruns", S_IRUSR,
+				   kmemtrace_dir, &kmemtrace_buf_overruns);
+	if (!kmemtrace_overruns_dentry || !kmemtrace_abi_version_dentry)
+		goto cleanup;
+
+	kmemtrace_enabled_dentry =
+		debugfs_create_file("enabled", S_IRUSR | S_IWUSR,
+				    kmemtrace_dir, &kmemtrace_enabled,
+				    &kmemtrace_enabled_fops);
+	if (!kmemtrace_enabled_dentry)
+		goto cleanup;
+
+	if (relay_late_setup_files(kmemtrace_chan, "cpu", kmemtrace_dir))
+		goto cleanup;
+
+	printk(KERN_INFO "kmemtrace: fully up.\n");
+
+	return 0;
+
+cleanup:
+	kmemtrace_cleanup();
+failed:
+	return 1;
+}
+late_initcall(kmemtrace_setup_late);
+
+static int __init kmemtrace_set_boot_enabled(char *str)
+{
+	if (!str)
+		return -EINVAL;
+
+	if (!strcmp(str, "yes"))
+		kmemtrace_enabled = 1;
+	else if (!strcmp(str, "no"))
+		kmemtrace_enabled = 0;
+	else
+		return -EINVAL;
+
+	return 0;
+}
+early_param("kmemtrace.enable", kmemtrace_set_boot_enabled);
+
+static int __init kmemtrace_set_subbufs(char *str)
+{
+	get_option(&str, &kmemtrace_n_subbufs);
+	return 0;
+}
+early_param("kmemtrace.subbufs", kmemtrace_set_subbufs);
+
+void kmemtrace_init(void)
+{
+	if (!kmemtrace_enabled)
+		return;
+
+	if (!kmemtrace_n_subbufs)
+		kmemtrace_n_subbufs = KMEMTRACE_DEF_N_SUBBUFS;
+
+	kmemtrace_chan = relay_open(NULL, NULL, KMEMTRACE_SUBBUF_SIZE,
+				    kmemtrace_n_subbufs, &relay_callbacks,
+				    NULL);
+	if (unlikely(!kmemtrace_chan)) {
+		printk(KERN_ERR "kmemtrace: could not open relay channel.\n");
+		return;
+	}
+
+	if (unlikely(kmemtrace_start_probes()))
+		goto probe_fail;
+
+	printk(KERN_INFO "kmemtrace: early init successful.\n");
+
+	return;
+
+probe_fail:
+	printk(KERN_ERR "kmemtrace: could not register marker probes!\n");
+	kmemtrace_cleanup();
+}
+