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