poke_loop_backed_fs.sh

# Show the mountpoint for the loopbacked fs
mount |grep zero; 

# Meminfo stats
cat /proc/meminfo | egrep -i "dirty|cache"; 

# Give humans a chance to run dd in another window
echo -e "\n**Sleeping for 10.. Waiting for I/O**\n"; 
sleep 10; 

# Meminfo stats
cat /proc/meminfo | egrep -i "dirty|cache"; 
echo -e "\n****\n"; 

# What does the world look like if we view the loopback fs via VFS (which effectively get it's results from the pagecache)
ls -lisa /tmp/bah;
echo -e "\n****\n"; 


# Meminfo stats
cat /proc/meminfo | egrep -i "dirty|cach|buff"; 
echo -e "\n****\n"; 

# What the actual backing file has (Reading the <real> disk data)
echo ls -l | /sbin/debugfs /tmp/zeros;
echo -e "\n\n****\n"; 

# How much of our backing file is in the pagecache
echo -e "\n****\n"; 
fincore /tmp/zeros; 

# Kicking out the file from the pagecache
echo -e "\n****\n"; 
fadvise /tmp/zeros POSIX_FADV_DONTNEED; 

# More stats
echo -e "\n****\n"; 
cat /proc/meminfo | egrep -i "dirty|cach|buff"; 

# Wake up pdflush and wait for it to flush dirty pages to the <real> hard disk
sync;
echo -e "\n*** Sleeping for 10.***\n";
sleep 10; 
echo -e "\n****\n"; 

# Show whether we were able to evict the backing file from the page cache
fincore /tmp/zeros; 
echo -e "\n****\n"; 

# Read the backing file contents
echo ls -l |/sbin/debugfs /tmp/zeros ; 
echo -e "\n****\n"; 

# Last bunch of stats
cat /proc/meminfo | egrep -i "dirty|cach|buff"; 
echo -e "\n****\n";