Analyze contiguous physical memory chunks that mmap system call gives

physmem_alloc_analysis/README.md

+
+# physmem_alloc_analysis: Physical memory allocation analysis
+
+This directory contains code to profile physical memory allocation
+for mmap, and analyze how contiguous the assigned physical frames are.
+This analysis is useful for evaluating the feasibility of double-sided
+rowhammering when there is no permission to access `/proc/self/pagemap`. 
+
+## How to run the program
+
+To compile and run the profiler:
+
+```
+./make.sh
+./physmem_alloc_profiler [-a alloc_size] [-s sleep_sec]
+```
+
+The profiler mmaps a chunk of memory of `alloc_size` (pages) each time,
+computes the assigned physical frames using `/proc/pid/pagemap` interface,
+and munmaps it. It then sleeps `sleep_sec` (seconds) before the next iteration. 
+The program loops infinitely so manual Control-C is needed to stop it. 
+A file named `physmem_alloc_results` is generated to record the assigned 
+physical frame numbers.
+
+To analyze the results, run:
+
+```
+./analyze.sh
+```
+
+This takes `physmem_alloc_results` as input and produces another file: 
+`contiguous_results`. As output, it shows the content of `contiguous_results`
+and invokes gnuplot for plotting as well.
+
+## Output format
+
+For `physmem_alloc_results`, each line contains information for each mmap
+allocation. The assigned physical frame numbers of each page are separated 
+by space.
+
+For `contiguous_results` (which is also shown as output for analyze.sh),
+each line is of the following format:
+
+```
+size    count   size_total    fraction
+```
+
+where:
+
+* `size` is the size (in number of pages) of virtual memory area that 
+  assigned with contiguous physical frames.
+
+* `count` is the number of times such virtual memory area appears.
+
+* `size_total` = `size` * `count`, i.e., it is the total size 
+  (in number of pages) for such memory area.
+
+* `fraction` = `size_total` / `alloc_total`, where `alloc_total` is
+  the sum of `size_total` of all rows. Therefore, `fraction` means
+  out of all virtual pages, what fraction of them are inside an area
+  of `size` pages whose underlying physical memory frames are contiguous.
+