+++ /dev/null
- kmemtrace - Kernel Memory Tracer
-
- by Eduard - Gabriel Munteanu
- <eduard.munteanu@linux360.ro>
-
-I. Introduction
-===============
-
-kmemtrace helps kernel developers figure out two things:
-1) how different allocators (SLAB, SLUB etc.) perform
-2) how kernel code allocates memory and how much
-
-To do this, we trace every allocation and export information to the userspace
-through the relay interface. We export things such as the number of requested
-bytes, the number of bytes actually allocated (i.e. including internal
-fragmentation), whether this is a slab allocation or a plain kmalloc() and so
-on.
-
-The actual analysis is performed by a userspace tool (see section III for
-details on where to get it from). It logs the data exported by the kernel,
-processes it and (as of writing this) can provide the following information:
-- the total amount of memory allocated and fragmentation per call-site
-- the amount of memory allocated and fragmentation per allocation
-- total memory allocated and fragmentation in the collected dataset
-- number of cross-CPU allocation and frees (makes sense in NUMA environments)
-
-Moreover, it can potentially find inconsistent and erroneous behavior in
-kernel code, such as using slab free functions on kmalloc'ed memory or
-allocating less memory than requested (but not truly failed allocations).
-
-kmemtrace also makes provisions for tracing on some arch and analysing the
-data on another.
-
-II. Design and goals
-====================
-
-kmemtrace was designed to handle rather large amounts of data. Thus, it uses
-the relay interface to export whatever is logged to userspace, which then
-stores it. Analysis and reporting is done asynchronously, that is, after the
-data is collected and stored. By design, it allows one to log and analyse
-on different machines and different arches.
-
-As of writing this, the ABI is not considered stable, though it might not
-change much. However, no guarantees are made about compatibility yet. When
-deemed stable, the ABI should still allow easy extension while maintaining
-backward compatibility. This is described further in Documentation/ABI.
-
-Summary of design goals:
- - allow logging and analysis to be done across different machines
- - be fast and anticipate usage in high-load environments (*)
- - be reasonably extensible
- - make it possible for GNU/Linux distributions to have kmemtrace
- included in their repositories
-
-(*) - one of the reasons Pekka Enberg's original userspace data analysis
- tool's code was rewritten from Perl to C (although this is more than a
- simple conversion)
-
-
-III. Quick usage guide
-======================
-
-1) Get a kernel that supports kmemtrace and build it accordingly (i.e. enable
-CONFIG_KMEMTRACE).
-
-2) Get the userspace tool and build it:
-$ git clone git://repo.or.cz/kmemtrace-user.git # current repository
-$ cd kmemtrace-user/
-$ ./autogen.sh
-$ ./configure
-$ make
-
-3) Boot the kmemtrace-enabled kernel if you haven't, preferably in the
-'single' runlevel (so that relay buffers don't fill up easily), and run
-kmemtrace:
-# '$' does not mean user, but root here.
-$ mount -t debugfs none /sys/kernel/debug
-$ mount -t proc none /proc
-$ cd path/to/kmemtrace-user/
-$ ./kmemtraced
-Wait a bit, then stop it with CTRL+C.
-$ cat /sys/kernel/debug/kmemtrace/total_overruns # Check if we didn't
- # overrun, should
- # be zero.
-$ (Optionally) [Run kmemtrace_check separately on each cpu[0-9]*.out file to
- check its correctness]
-$ ./kmemtrace-report
-
-Now you should have a nice and short summary of how the allocator performs.
-
-IV. FAQ and known issues
-========================
-
-Q: 'cat /sys/kernel/debug/kmemtrace/total_overruns' is non-zero, how do I fix
-this? Should I worry?
-A: If it's non-zero, this affects kmemtrace's accuracy, depending on how
-large the number is. You can fix it by supplying a higher
-'kmemtrace.subbufs=N' kernel parameter.
----
-
-Q: kmemtrace_check reports errors, how do I fix this? Should I worry?
-A: This is a bug and should be reported. It can occur for a variety of
-reasons:
- - possible bugs in relay code
- - possible misuse of relay by kmemtrace
- - timestamps being collected unorderly
-Or you may fix it yourself and send us a patch.
----
-
-Q: kmemtrace_report shows many errors, how do I fix this? Should I worry?
-A: This is a known issue and I'm working on it. These might be true errors
-in kernel code, which may have inconsistent behavior (e.g. allocating memory
-with kmem_cache_alloc() and freeing it with kfree()). Pekka Enberg pointed
-out this behavior may work with SLAB, but may fail with other allocators.
-
-It may also be due to lack of tracing in some unusual allocator functions.
-
-We don't want bug reports regarding this issue yet.
----
-
-V. See also
-===========
-
-Documentation/kernel-parameters.txt
-Documentation/ABI/testing/debugfs-kmemtrace
-
+++ /dev/null
-/*
- * Memory allocator tracing
- *
- * Copyright (C) 2008 Eduard - Gabriel Munteanu
- * Copyright (C) 2008 Pekka Enberg <penberg@cs.helsinki.fi>
- * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
- */
-
-#include <linux/tracepoint.h>
-#include <linux/seq_file.h>
-#include <linux/debugfs.h>
-#include <linux/dcache.h>
-#include <linux/fs.h>
-
-#include <linux/kmemtrace.h>
-
-#include "trace_output.h"
-#include "trace.h"
-
-/* Select an alternative, minimalistic output than the original one */
-#define TRACE_KMEM_OPT_MINIMAL 0x1
-
-static struct tracer_opt kmem_opts[] = {
- /* Default disable the minimalistic output */
- { TRACER_OPT(kmem_minimalistic, TRACE_KMEM_OPT_MINIMAL) },
- { }
-};
-
-static struct tracer_flags kmem_tracer_flags = {
- .val = 0,
- .opts = kmem_opts
-};
-
-static struct trace_array *kmemtrace_array;
-
-/* Trace allocations */
-static inline void kmemtrace_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,
- int node)
-{
- struct ftrace_event_call *call = &event_kmem_alloc;
- struct trace_array *tr = kmemtrace_array;
- struct kmemtrace_alloc_entry *entry;
- struct ring_buffer_event *event;
-
- event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
- if (!event)
- return;
-
- entry = ring_buffer_event_data(event);
- tracing_generic_entry_update(&entry->ent, 0, 0);
-
- entry->ent.type = TRACE_KMEM_ALLOC;
- entry->type_id = type_id;
- entry->call_site = call_site;
- entry->ptr = ptr;
- entry->bytes_req = bytes_req;
- entry->bytes_alloc = bytes_alloc;
- entry->gfp_flags = gfp_flags;
- entry->node = node;
-
- if (!filter_check_discard(call, entry, tr->buffer, event))
- ring_buffer_unlock_commit(tr->buffer, event);
-
- trace_wake_up();
-}
-
-static inline void kmemtrace_free(enum kmemtrace_type_id type_id,
- unsigned long call_site,
- const void *ptr)
-{
- struct ftrace_event_call *call = &event_kmem_free;
- struct trace_array *tr = kmemtrace_array;
- struct kmemtrace_free_entry *entry;
- struct ring_buffer_event *event;
-
- event = ring_buffer_lock_reserve(tr->buffer, sizeof(*entry));
- if (!event)
- return;
- entry = ring_buffer_event_data(event);
- tracing_generic_entry_update(&entry->ent, 0, 0);
-
- entry->ent.type = TRACE_KMEM_FREE;
- entry->type_id = type_id;
- entry->call_site = call_site;
- entry->ptr = ptr;
-
- if (!filter_check_discard(call, entry, tr->buffer, event))
- ring_buffer_unlock_commit(tr->buffer, event);
-
- trace_wake_up();
-}
-
-static void kmemtrace_kmalloc(void *ignore,
- unsigned long call_site,
- const void *ptr,
- size_t bytes_req,
- size_t bytes_alloc,
- gfp_t gfp_flags)
-{
- kmemtrace_alloc(KMEMTRACE_TYPE_KMALLOC, call_site, ptr,
- bytes_req, bytes_alloc, gfp_flags, -1);
-}
-
-static void kmemtrace_kmem_cache_alloc(void *ignore,
- unsigned long call_site,
- const void *ptr,
- size_t bytes_req,
- size_t bytes_alloc,
- gfp_t gfp_flags)
-{
- kmemtrace_alloc(KMEMTRACE_TYPE_CACHE, call_site, ptr,
- bytes_req, bytes_alloc, gfp_flags, -1);
-}
-
-static void kmemtrace_kmalloc_node(void *ignore,
- unsigned long call_site,
- const void *ptr,
- size_t bytes_req,
- size_t bytes_alloc,
- gfp_t gfp_flags,
- int node)
-{
- kmemtrace_alloc(KMEMTRACE_TYPE_KMALLOC, call_site, ptr,
- bytes_req, bytes_alloc, gfp_flags, node);
-}
-
-static void kmemtrace_kmem_cache_alloc_node(void *ignore,
- unsigned long call_site,
- const void *ptr,
- size_t bytes_req,
- size_t bytes_alloc,
- gfp_t gfp_flags,
- int node)
-{
- kmemtrace_alloc(KMEMTRACE_TYPE_CACHE, call_site, ptr,
- bytes_req, bytes_alloc, gfp_flags, node);
-}
-
-static void
-kmemtrace_kfree(void *ignore, unsigned long call_site, const void *ptr)
-{
- kmemtrace_free(KMEMTRACE_TYPE_KMALLOC, call_site, ptr);
-}
-
-static void kmemtrace_kmem_cache_free(void *ignore,
- unsigned long call_site, const void *ptr)
-{
- kmemtrace_free(KMEMTRACE_TYPE_CACHE, call_site, ptr);
-}
-
-static int kmemtrace_start_probes(void)
-{
- int err;
-
- err = register_trace_kmalloc(kmemtrace_kmalloc, NULL);
- if (err)
- return err;
- err = register_trace_kmem_cache_alloc(kmemtrace_kmem_cache_alloc, NULL);
- if (err)
- return err;
- err = register_trace_kmalloc_node(kmemtrace_kmalloc_node, NULL);
- if (err)
- return err;
- err = register_trace_kmem_cache_alloc_node(kmemtrace_kmem_cache_alloc_node, NULL);
- if (err)
- return err;
- err = register_trace_kfree(kmemtrace_kfree, NULL);
- if (err)
- return err;
- err = register_trace_kmem_cache_free(kmemtrace_kmem_cache_free, NULL);
-
- return err;
-}
-
-static void kmemtrace_stop_probes(void)
-{
- unregister_trace_kmalloc(kmemtrace_kmalloc, NULL);
- unregister_trace_kmem_cache_alloc(kmemtrace_kmem_cache_alloc, NULL);
- unregister_trace_kmalloc_node(kmemtrace_kmalloc_node, NULL);
- unregister_trace_kmem_cache_alloc_node(kmemtrace_kmem_cache_alloc_node, NULL);
- unregister_trace_kfree(kmemtrace_kfree, NULL);
- unregister_trace_kmem_cache_free(kmemtrace_kmem_cache_free, NULL);
-}
-
-static int kmem_trace_init(struct trace_array *tr)
-{
- kmemtrace_array = tr;
-
- tracing_reset_online_cpus(tr);
-
- kmemtrace_start_probes();
-
- return 0;
-}
-
-static void kmem_trace_reset(struct trace_array *tr)
-{
- kmemtrace_stop_probes();
-}
-
-static void kmemtrace_headers(struct seq_file *s)
-{
- /* Don't need headers for the original kmemtrace output */
- if (!(kmem_tracer_flags.val & TRACE_KMEM_OPT_MINIMAL))
- return;
-
- seq_printf(s, "#\n");
- seq_printf(s, "# ALLOC TYPE REQ GIVEN FLAGS "
- " POINTER NODE CALLER\n");
- seq_printf(s, "# FREE | | | | "
- " | | | |\n");
- seq_printf(s, "# |\n\n");
-}
-
-/*
- * The following functions give the original output from kmemtrace,
- * plus the origin CPU, since reordering occurs in-kernel now.
- */
-
-#define KMEMTRACE_USER_ALLOC 0
-#define KMEMTRACE_USER_FREE 1
-
-struct kmemtrace_user_event {
- u8 event_id;
- u8 type_id;
- u16 event_size;
- u32 cpu;
- u64 timestamp;
- unsigned long call_site;
- unsigned long ptr;
-};
-
-struct kmemtrace_user_event_alloc {
- size_t bytes_req;
- size_t bytes_alloc;
- unsigned gfp_flags;
- int node;
-};
-
-static enum print_line_t
-kmemtrace_print_alloc(struct trace_iterator *iter, int flags,
- struct trace_event *event)
-{
- struct trace_seq *s = &iter->seq;
- struct kmemtrace_alloc_entry *entry;
- int ret;
-
- trace_assign_type(entry, iter->ent);
-
- ret = trace_seq_printf(s, "type_id %d call_site %pF ptr %lu "
- "bytes_req %lu bytes_alloc %lu gfp_flags %lu node %d\n",
- entry->type_id, (void *)entry->call_site, (unsigned long)entry->ptr,
- (unsigned long)entry->bytes_req, (unsigned long)entry->bytes_alloc,
- (unsigned long)entry->gfp_flags, entry->node);
-
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- return TRACE_TYPE_HANDLED;
-}
-
-static enum print_line_t
-kmemtrace_print_free(struct trace_iterator *iter, int flags,
- struct trace_event *event)
-{
- struct trace_seq *s = &iter->seq;
- struct kmemtrace_free_entry *entry;
- int ret;
-
- trace_assign_type(entry, iter->ent);
-
- ret = trace_seq_printf(s, "type_id %d call_site %pF ptr %lu\n",
- entry->type_id, (void *)entry->call_site,
- (unsigned long)entry->ptr);
-
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
- return TRACE_TYPE_HANDLED;
-}
-
-static enum print_line_t
-kmemtrace_print_alloc_user(struct trace_iterator *iter, int flags,
- struct trace_event *event)
-{
- struct trace_seq *s = &iter->seq;
- struct kmemtrace_alloc_entry *entry;
- struct kmemtrace_user_event *ev;
- struct kmemtrace_user_event_alloc *ev_alloc;
-
- trace_assign_type(entry, iter->ent);
-
- ev = trace_seq_reserve(s, sizeof(*ev));
- if (!ev)
- return TRACE_TYPE_PARTIAL_LINE;
-
- ev->event_id = KMEMTRACE_USER_ALLOC;
- ev->type_id = entry->type_id;
- ev->event_size = sizeof(*ev) + sizeof(*ev_alloc);
- ev->cpu = iter->cpu;
- ev->timestamp = iter->ts;
- ev->call_site = entry->call_site;
- ev->ptr = (unsigned long)entry->ptr;
-
- ev_alloc = trace_seq_reserve(s, sizeof(*ev_alloc));
- if (!ev_alloc)
- return TRACE_TYPE_PARTIAL_LINE;
-
- ev_alloc->bytes_req = entry->bytes_req;
- ev_alloc->bytes_alloc = entry->bytes_alloc;
- ev_alloc->gfp_flags = entry->gfp_flags;
- ev_alloc->node = entry->node;
-
- return TRACE_TYPE_HANDLED;
-}
-
-static enum print_line_t
-kmemtrace_print_free_user(struct trace_iterator *iter, int flags,
- struct trace_event *event)
-{
- struct trace_seq *s = &iter->seq;
- struct kmemtrace_free_entry *entry;
- struct kmemtrace_user_event *ev;
-
- trace_assign_type(entry, iter->ent);
-
- ev = trace_seq_reserve(s, sizeof(*ev));
- if (!ev)
- return TRACE_TYPE_PARTIAL_LINE;
-
- ev->event_id = KMEMTRACE_USER_FREE;
- ev->type_id = entry->type_id;
- ev->event_size = sizeof(*ev);
- ev->cpu = iter->cpu;
- ev->timestamp = iter->ts;
- ev->call_site = entry->call_site;
- ev->ptr = (unsigned long)entry->ptr;
-
- return TRACE_TYPE_HANDLED;
-}
-
-/* The two other following provide a more minimalistic output */
-static enum print_line_t
-kmemtrace_print_alloc_compress(struct trace_iterator *iter)
-{
- struct kmemtrace_alloc_entry *entry;
- struct trace_seq *s = &iter->seq;
- int ret;
-
- trace_assign_type(entry, iter->ent);
-
- /* Alloc entry */
- ret = trace_seq_printf(s, " + ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Type */
- switch (entry->type_id) {
- case KMEMTRACE_TYPE_KMALLOC:
- ret = trace_seq_printf(s, "K ");
- break;
- case KMEMTRACE_TYPE_CACHE:
- ret = trace_seq_printf(s, "C ");
- break;
- case KMEMTRACE_TYPE_PAGES:
- ret = trace_seq_printf(s, "P ");
- break;
- default:
- ret = trace_seq_printf(s, "? ");
- }
-
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Requested */
- ret = trace_seq_printf(s, "%4zu ", entry->bytes_req);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Allocated */
- ret = trace_seq_printf(s, "%4zu ", entry->bytes_alloc);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Flags
- * TODO: would be better to see the name of the GFP flag names
- */
- ret = trace_seq_printf(s, "%08x ", entry->gfp_flags);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Pointer to allocated */
- ret = trace_seq_printf(s, "0x%tx ", (ptrdiff_t)entry->ptr);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Node and call site*/
- ret = trace_seq_printf(s, "%4d %pf\n", entry->node,
- (void *)entry->call_site);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- return TRACE_TYPE_HANDLED;
-}
-
-static enum print_line_t
-kmemtrace_print_free_compress(struct trace_iterator *iter)
-{
- struct kmemtrace_free_entry *entry;
- struct trace_seq *s = &iter->seq;
- int ret;
-
- trace_assign_type(entry, iter->ent);
-
- /* Free entry */
- ret = trace_seq_printf(s, " - ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Type */
- switch (entry->type_id) {
- case KMEMTRACE_TYPE_KMALLOC:
- ret = trace_seq_printf(s, "K ");
- break;
- case KMEMTRACE_TYPE_CACHE:
- ret = trace_seq_printf(s, "C ");
- break;
- case KMEMTRACE_TYPE_PAGES:
- ret = trace_seq_printf(s, "P ");
- break;
- default:
- ret = trace_seq_printf(s, "? ");
- }
-
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Skip requested/allocated/flags */
- ret = trace_seq_printf(s, " ");
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Pointer to allocated */
- ret = trace_seq_printf(s, "0x%tx ", (ptrdiff_t)entry->ptr);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- /* Skip node and print call site*/
- ret = trace_seq_printf(s, " %pf\n", (void *)entry->call_site);
- if (!ret)
- return TRACE_TYPE_PARTIAL_LINE;
-
- return TRACE_TYPE_HANDLED;
-}
-
-static enum print_line_t kmemtrace_print_line(struct trace_iterator *iter)
-{
- struct trace_entry *entry = iter->ent;
-
- if (!(kmem_tracer_flags.val & TRACE_KMEM_OPT_MINIMAL))
- return TRACE_TYPE_UNHANDLED;
-
- switch (entry->type) {
- case TRACE_KMEM_ALLOC:
- return kmemtrace_print_alloc_compress(iter);
- case TRACE_KMEM_FREE:
- return kmemtrace_print_free_compress(iter);
- default:
- return TRACE_TYPE_UNHANDLED;
- }
-}
-
-static struct trace_event_functions kmem_trace_alloc_funcs = {
- .trace = kmemtrace_print_alloc,
- .binary = kmemtrace_print_alloc_user,
-};
-
-static struct trace_event kmem_trace_alloc = {
- .type = TRACE_KMEM_ALLOC,
- .funcs = &kmem_trace_alloc_funcs,
-};
-
-static struct trace_event_functions kmem_trace_free_funcs = {
- .trace = kmemtrace_print_free,
- .binary = kmemtrace_print_free_user,
-};
-
-static struct trace_event kmem_trace_free = {
- .type = TRACE_KMEM_FREE,
- .funcs = &kmem_trace_free_funcs,
-};
-
-static struct tracer kmem_tracer __read_mostly = {
- .name = "kmemtrace",
- .init = kmem_trace_init,
- .reset = kmem_trace_reset,
- .print_line = kmemtrace_print_line,
- .print_header = kmemtrace_headers,
- .flags = &kmem_tracer_flags
-};
-
-void kmemtrace_init(void)
-{
- /* earliest opportunity to start kmem tracing */
-}
-
-static int __init init_kmem_tracer(void)
-{
- if (!register_ftrace_event(&kmem_trace_alloc)) {
- pr_warning("Warning: could not register kmem events\n");
- return 1;
- }
-
- if (!register_ftrace_event(&kmem_trace_free)) {
- pr_warning("Warning: could not register kmem events\n");
- return 1;
- }
-
- if (register_tracer(&kmem_tracer) != 0) {
- pr_warning("Warning: could not register the kmem tracer\n");
- return 1;
- }
-
- return 0;
-}
-device_initcall(init_kmem_tracer);
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