mirror of
https://github.com/linuxkit/linuxkit.git
synced 2025-10-31 11:45:55 +00:00
b47c64f525
This commits an initial version of the Memorizer tracing tool. It collects and outputs detailed data on the objects (traced from kmalloc/kmem_cache_alloc) and accesses, tracking the context of each event with respect to thread ID, program counter, and for allocations name of process. Signed-off-by: Nathan Dautenhahn <ndd@cis.upenn.edu>
93 lines
2.9 KiB
Plaintext
93 lines
2.9 KiB
Plaintext
|
|
+--------------------------------------------------+
|
|
| Memorizer: Kernel Memory Access Patterns (KMAPs) |
|
|
+--------------------------------------------------+
|
|
|
|
Introduction
|
|
============
|
|
|
|
Memorizer is a tool to record information about access to kernel objects:
|
|
specifically, it counts memory accesses from distinct IP addresses in the
|
|
kernel source and also the PID that accessed, thereby providing spatial and
|
|
temporal dimensions.
|
|
|
|
Interface via debugfs
|
|
=====================
|
|
|
|
The tool has a very simple interface at the moment. It can:
|
|
|
|
- Print out some statistics about memory allocations and memory accesses
|
|
- Control enable/disable of memory object allocation tracking and memory access
|
|
tracing
|
|
- Print the KMAP using the debugfs file system
|
|
|
|
Enable object allocation tracking:
|
|
```bash
|
|
echo 1 > /sys/kernel/debug/memorizer/memorizer_enabled
|
|
```
|
|
|
|
Enable object access tracking:
|
|
```bash
|
|
echo 1 > /sys/kernel/debug/memorizer/memorizer_log_access
|
|
```
|
|
|
|
Show allocation statistics:
|
|
```bash
|
|
cat /sys/kernel/debug/memorizer/show_stats
|
|
```
|
|
|
|
Clear free'd objects:
|
|
```bash
|
|
echo 1 > /sys/kernel/debug/memorizer/clear_object_list
|
|
```
|
|
|
|
Using Memorizer to Collect KMAPs
|
|
================================
|
|
|
|
Memorizer lacks push style logging and clearing of the object lists, therefore
|
|
it has the propensity of overflowing memory. The only way to manage the log and
|
|
current set of objects is to manually clear and print the KMAPs.
|
|
|
|
Therefore, a typical run using memorizer to create KMAPs includes:
|
|
|
|
```bash
|
|
# mount the debugfs filesystem if it isn't already
|
|
mount -t debugfs nodev /sys/kernel/debug
|
|
# clear free objects: the current system traces from boot with a lot of
|
|
# uninteresting data
|
|
echo 1 > /sys/kernel/debug/clear_object_list
|
|
# enable memorizer object access tracking, which by default is off
|
|
echo 1 > /sys/kernel/debug/memorizer_log_access
|
|
# Now run whatever test
|
|
tar zcf something.tar.gz /somedir &
|
|
ssh u@h:/somefile
|
|
...
|
|
# Disable access logging
|
|
echo 0 > /sys/kernel/debug/memorizer/memorizer_log_access
|
|
# Disable memorizer object tracking: isn't necessary but will reduce noise
|
|
echo 0 > /sys/kernel/debug/memorizer/memorizer_enabled
|
|
# Cat the results: make sure to pipe to something
|
|
cat /sys/kernel/debug/memorizer/kmap > test.kmap
|
|
```
|
|
|
|
Output Format
|
|
=============
|
|
|
|
Memorizer outputs data as text, which may change if space is a problem. The
|
|
format of the kmap file is as follows:
|
|
|
|
alloc_ip,pid,obj_va_ptr,size,alloc_jiffies,free_jiffies,free_ip,executable
|
|
access_ip,access_pid,write_count,read_count
|
|
access_ip,access_pid,write_count,read_count
|
|
access_ip,access_pid,write_count,read_count
|
|
...
|
|
...
|
|
|
|
There are a few special error codes:
|
|
|
|
- Not all free_ip's could be obtained correctly and therefore some of these
|
|
will be 0.
|
|
- There is a bug where we insert into the live object map over another
|
|
allocation, this implies that we are missing a free. So for now we mark
|
|
the free_ip as 0xDEADBEEF.
|