add slabratetop (iovisor#759)

README.md

@@ -99,6 +99,7 @@ Examples:
 - tools/[gethostlatency](tools/gethostlatency.py): Show latency for getaddrinfo/gethostbyname[2] calls. [Examples](tools/gethostlatency_example.txt).
 - tools/[hardirqs](tools/hardirqs.py): Measure hard IRQ (hard interrupt) event time. [Examples](tools/hardirqs_example.txt).
 - tools/[killsnoop](tools/killsnoop.py): Trace signals issued by the kill() syscall. [Examples](tools/killsnoop_example.txt).
+- tools/[slabratetop](tools/slabratetop.py): Kernel SLAB/SLUB memory cache allocation rate top. [Examples](tools/slabratetop_example.txt).
 - tools/[mdflush](tools/mdflush.py): Trace md flush events. [Examples](tools/mdflush_example.txt).
 - tools/[mysqld_qslower](tools/mysqld_qslower.py): Trace MySQL server queries slower than a threshold. [Examples](tools/mysqld_qslower_example.txt).
 - tools/[memleak](tools/memleak.py): Display outstanding memory allocations to find memory leaks. [Examples](tools/memleak_example.txt).

man/man8/slabratetop.8

@@ -0,0 +1,76 @@
+.TH slabratetop 8 "2016-10-17" "USER COMMANDS"
+.SH NAME
+slabratetop \- Kernel SLAB/SLUB memory cache allocation rate top.
+Uses Linux BPF/bcc.
+.SH SYNOPSIS
+.B slabratetop [\-h] [\-C] [\-r MAXROWS] [interval] [count]
+.SH DESCRIPTION
+This is top for the the rate of kernel SLAB/SLUB memory allocations.
+It works by tracing kmem_cache_alloc() calls, a commonly used interface for
+kernel memory allocation (SLAB or SLUB). It summarizes the rate and total bytes
+allocated of these calls per interval: the activity. Compare this to
+slabtop(1), which shows the current static volume of the caches.
+
+This tool uses kernel dynamic tracing of the kmem_cache_alloc() function.
+
+Since this uses BPF, only the root user can use this tool.
+.SH REQUIREMENTS
+CONFIG_BPF and bcc.
+.SH OPTIONS
+.TP
+\-C
+Don't clear the screen.
+.TP
+\-r MAXROWS
+Maximum number of rows to print. Default is 20.
+.TP
+interval
+Interval between updates, seconds.
+.TP
+count
+Number of interval summaries.
+.SH EXAMPLES
+.TP
+Summarize active kernel SLAB/SLUB calls (kmem_cache_alloc()), showing the top 20 caches every second:
+#
+.B slabratetop
+.TP
+Don't clear the screen, and top 8 rows only:
+#
+.B slabratetop -Cr 8
+.TP
+5 second summaries, 10 times only:
+#
+.B slabratetop 5 10
+.SH FIELDS
+.TP
+loadavg:
+The contents of /proc/loadavg
+.TP
+CACHE
+Kernel cache name.
+.TP
+ALLOCS
+Allocations (number of calls).
+.TP
+BYTES
+Total bytes allocated.
+.SH OVERHEAD
+If kmem_cache_alloc() is called at a high rate (eg, >100k/second) the overhead
+of this tool might begin to be measurable. The rate can be seen in the ALLOCS
+column of the output.
+.SH SOURCE
+This is from bcc.
+.IP
+https://github.com/iovisor/bcc
+.PP
+Also look in the bcc distribution for a companion _examples.txt file containing
+example usage, output, and commentary for this tool.
+.SH OS
+Linux
+.SH STABILITY
+Unstable - in development.
+.SH AUTHOR
+Brendan Gregg
+.SH SEE ALSO
+slabtop(1)

tools/slabratetop.py

@@ -0,0 +1,133 @@
+#!/usr/bin/python
+# @lint-avoid-python-3-compatibility-imports
+#
+# slabratetop Summarize kmem_cache_alloc() calls.
+# For Linux, uses BCC, eBPF.
+#
+# USAGE: slabratetop [-h] [-C] [-r MAXROWS] [interval] [count]
+#
+# This uses in-kernel BPF maps to store cache summaries for efficiency.
+#
+# SEE ALSO: slabtop(1), which shows the cache volumes.
+#
+# Copyright 2016 Netflix, Inc.
+# Licensed under the Apache License, Version 2.0 (the "License")
+#
+# 15-Oct-2016 Brendan Gregg Created this.
+
+from __future__ import print_function
+from bcc import BPF
+from time import sleep, strftime
+import argparse
+import signal
+from subprocess import call
+
+# arguments
+examples = """examples:
+ ./slabratetop # kmem_cache_alloc() top, 1 second refresh
+ ./slabratetop -C # don't clear the screen
+ ./slabratetop 5 # 5 second summaries
+ ./slabratetop 5 10 # 5 second summaries, 10 times only
+"""
+parser = argparse.ArgumentParser(
+ description="Kernel SLAB/SLUB memory cache allocation rate top",
+ formatter_class=argparse.RawDescriptionHelpFormatter,
+ epilog=examples)
+parser.add_argument("-C", "--noclear", action="store_true",
+ help="don't clear the screen")
+parser.add_argument("-r", "--maxrows", default=20,
+ help="maximum rows to print, default 20")
+parser.add_argument("interval", nargs="?", default=1,
+ help="output interval, in seconds")
+parser.add_argument("count", nargs="?", default=99999999,
+ help="number of outputs")
+args = parser.parse_args()
+interval = int(args.interval)
+countdown = int(args.count)
+maxrows = int(args.maxrows)
+clear = not int(args.noclear)
+debug = 0
+
+# linux stats
+loadavg = "/proc/loadavg"
+
+# signal handler
+def signal_ignore(signal, frame):
+ print()
+
+# define BPF program
+bpf_text = """
+#include <uapi/linux/ptrace.h>
+#include <linux/mm.h>
+#include <linux/slab.h>
+#include <linux/slub_def.h>
+
+#define CACHE_NAME_SIZE 32
+
+// the key for the output summary
+struct info_t {
+ char name[CACHE_NAME_SIZE];
+};
+
+// the value of the output summary
+struct val_t {
+ u64 count;
+ u64 size;
+};
+
+BPF_HASH(counts, struct info_t, struct val_t);
+
+int kprobe__kmem_cache_alloc(struct pt_regs *ctx, struct kmem_cache *cachep)
+{
+ struct info_t info = {};
+ bpf_probe_read(&info.name, sizeof(info.name), (void *)cachep->name);
+
+ struct val_t *valp, zero = {};
+ valp = counts.lookup_or_init(&info, &zero);
+ valp->count++;
+ valp->size += cachep->size;
+
+ return 0;
+}
+"""
+if debug:
+ print(bpf_text)
+
+# initialize BPF
+b = BPF(text=bpf_text)
+
+print('Tracing... Output every %d secs. Hit Ctrl-C to end' % interval)
+
+# output
+exiting = 0
+while 1:
+ try:
+ sleep(interval)
+ except KeyboardInterrupt:
+ exiting = 1
+
+ # header
+ if clear:
+ call("clear")
+ else:
+ print()
+ with open(loadavg) as stats:
+ print("%-8s loadavg: %s" % (strftime("%H:%M:%S"), stats.read()))
+ print("%-32s %6s %10s" % ("CACHE", "ALLOCS", "BYTES"))
+
+ # by-TID output
+ counts = b.get_table("counts")
+ line = 0
+ for k, v in reversed(sorted(counts.items(),
+ key=lambda counts: counts[1].size)):
+ print("%-32s %6d %10d" % (k.name, v.count, v.size))
+
+ line += 1
+ if line >= maxrows:
+ break
+ counts.clear()
+
+ countdown -= 1
+ if exiting or countdown == 0:
+ print("Detaching...")
+ exit()

tools/slabratetop_example.txt

@@ -0,0 +1,134 @@
+Demonstrations of slabratetop, the Linux eBPF/bcc version.
+
+
+slabratetop shows the rate of allocations and total bytes from the kernel
+memory allocation caches (SLAB or SLUB), in a top-like display that refreshes.
+For example:
+
+# ./slabratetop
+<screen clears>
+07:01:35 loadavg: 0.38 0.21 0.12 1/342 13297
+
+CACHE ALLOCS BYTES
+kmalloc-4096 3554 14557184
+kmalloc-256 2382 609536
+cred_jar 2568 493056
+anon_vma_chain 2007 128448
+anon_vma 972 77760
+sighand_cache 24 50688
+mm_struct 49 50176
+RAW 52 49920
+proc_inode_cache 59 38232
+signal_cache 24 26112
+dentry 135 25920
+sock_inode_cache 29 18560
+files_cache 24 16896
+inode_cache 13 7696
+TCP 2 3840
+pid 24 3072
+sigqueue 17 2720
+ext4_inode_cache 2 2160
+buffer_head 16 1664
+xfs_trans 5 1160
+
+By default the screen refreshes every one second, and only the top 20 caches
+are shown. These can be tuned with options: see USAGE (-h).
+
+The output above showed that the kmalloc-4096 cache allocated the most, about
+14 Mbytes during this interval. This is a generic cache; other caches have
+more meaningful names ("dentry", "TCP", "pid", etc).
+
+slabtop(1) is a similar tool that shows the current static volume and usage
+of the caches. slabratetop shows the active call rates and total size of the
+allocations.
+
+
+Since "kmalloc-4096" isn't very descriptive, I'm interested in seeing the
+kernel stacks that led to this allocation. In the future (maybe by now) the
+bcc trace tool could do this. As I'm writing this, it can't, so I'll use my
+older ftrace-based kprobe tool as a workarond. This is from my perf-tools
+collection: https://github.com/brendangregg/perf-tools.
+
+# ./perf-tools/bin/kprobe -s 'p:kmem_cache_alloc name=+0(+96(%di)):string' 'name == "kmalloc-4096' | head -100
+Tracing kprobe kmem_cache_alloc. Ctrl-C to end.
+ kprobe-3892 [002] d... 7888274.478331: kmem_cache_alloc: (kmem_cache_alloc+0x0/0x1b0) name="kmalloc-4096"
+ kprobe-3892 [002] d... 7888274.478333: <stack trace>
+ => kmem_cache_alloc
+ => user_path_at_empty
+ => vfs_fstatat
+ => SYSC_newstat
+ => SyS_newstat
+ => entry_SYSCALL_64_fastpath
+ kprobe-3892 [002] d... 7888274.478340: kmem_cache_alloc: (kmem_cache_alloc+0x0/0x1b0) name="kmalloc-4096"
+ kprobe-3892 [002] d... 7888274.478341: <stack trace>
+ => kmem_cache_alloc
+ => user_path_at_empty
+ => vfs_fstatat
+ => SYSC_newstat
+ => SyS_newstat
+ => entry_SYSCALL_64_fastpath
+ kprobe-3892 [002] d... 7888274.478345: kmem_cache_alloc: (kmem_cache_alloc+0x0/0x1b0) name="kmalloc-4096"
+ kprobe-3892 [002] d... 7888274.478346: <stack trace>
+ => kmem_cache_alloc
+ => user_path_at_empty
+ => vfs_fstatat
+ => SYSC_newstat
+ => SyS_newstat
+ => entry_SYSCALL_64_fastpath
+ kprobe-3892 [002] d... 7888274.478350: kmem_cache_alloc: (kmem_cache_alloc+0x0/0x1b0) name="kmalloc-4096"
+ kprobe-3892 [002] d... 7888274.478351: <stack trace>
+ => kmem_cache_alloc
+ => user_path_at_empty
+ => vfs_fstatat
+ => SYSC_newstat
+ => SyS_newstat
+ => entry_SYSCALL_64_fastpath
+ kprobe-3892 [002] d... 7888274.478355: kmem_cache_alloc: (kmem_cache_alloc+0x0/0x1b0) name="kmalloc-4096"
+ kprobe-3892 [002] d... 7888274.478355: <stack trace>
+ => kmem_cache_alloc
+ => user_path_at_empty
+ => vfs_fstatat
+ => SYSC_newstat
+ => SyS_newstat
+ => entry_SYSCALL_64_fastpath
+ kprobe-3892 [002] d... 7888274.478359: kmem_cache_alloc: (kmem_cache_alloc+0x0/0x1b0) name="kmalloc-4096"
+ kprobe-3892 [002] d... 7888274.478359: <stack trace>
+ => kmem_cache_alloc
+ => user_path_at_empty
+ => vfs_fstatat
+ => SYSC_newstat
+ => SyS_newstat
+ => entry_SYSCALL_64_fastpath
+[...]
+
+This is just an example so that you can see it's possible to dig further.
+Please don't copy-n-paste that kprobe command, as it's unlikely to work (the
+"+0(+96(%di))" text is specific to a kernel version and architecture).
+
+So these allocations are coming from user_path_at_empty(), which calls other
+functions (not seen in the stack: I suspect it's a tail-call compiler
+optimization).
+
+
+USAGE:
+
+# ./slabratetop -h
+usage: slabratetop [-h] [-C] [-r MAXROWS] [interval] [count]
+
+Kernel SLAB/SLUB memory cache allocation rate top
+
+positional arguments:
+ interval output interval, in seconds
+ count number of outputs
+
+optional arguments:
+ -h, --help show this help message and exit
+ -C, --noclear don't clear the screen
+ -r MAXROWS, --maxrows MAXROWS
+ maximum rows to print, default 20
+
+examples:
+ ./slabratetop # kmem_cache_alloc() top, 1 second refresh
+ ./slabratetop -C # don't clear the screen
+ ./slabratetop 5 # 5 second summaries
+ ./slabratetop 5 10 # 5 second summaries, 10 times only