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>

2 files changed, 336 insertions, 0 deletions

diff --git a/mm/Makefile b/mm/Makefile
index c06b45a1ff5f..3782eb66d4b3 100644
--- a/mm/Makefile
+++ b/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
diff --git a/mm/kmemtrace.c b/mm/kmemtrace.c
new file mode 100644
index 000000000000..83ad1cc71a92
--- /dev/null
+++ b/mm/kmemtrace.c
@@ -0,0 +1,335 @@
+/*
+ * 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();
+}
+