1. CS Honors Research: Memory Mapped files in Linux Checkpoint 1 Kousha Najafi Prof: Eddie Kohler Grad Student: Steve VanDeBogart 12.7.07

2. Research Topic Explore Linux memory-mapped-file system call performance. Find and Resolve inconstancies when compared to read system call

3. mmap vs read (Forwards old) 128MB rampreadmmap min4.81s8.29s max5.34s19.46s avg4.97s13.68s stdev0.17s4.95s Reading 256MB file on system with 128MB memory

4. mmap vs read (Forwards) 128MB rampreadmmap min5.19s8.64s max5.56s10.31s avg5.29s9.49s stdev0.11s.51s Reading 256MB file on system with 128MB memory

5. mmap vs read (Backwards old) 128MB rampreadmmap min23.20s17.20s max23.47s25.84s avg23.33s23.02s stdev0.08s3.32s Reading 256MB file on system with 128MB memory

6. mmap vs read (Backwards) 128MB rampreadmmap min23.85s14.36s max24.20s15.48s avg23.97s14.94s stdev0.11s.43s Reading 256MB file on system with 128MB memory

7. Previous Checkpoints Figure out what causes the slowdown Figure out what causes the inconsistencies Come up with theory to fix problem Try to code a patch to fix problem

8. Checkpoint Progress Figure out what causes the slowdown –Slowdown is probably due to the read-ahead mechanism used by mmap. Figure out what causes the inconsistencies –Seems to be caused by a random race condition involved with calling the read-ahead functions.

9. Checkpoints Revisions Figure out read-ahead slowdown Figure out race condition that causes timing inconsistencies Come up with theory to fix problem