I have a 4GB file that are just rows of sorted key,value pairs that I have "primed" into memory (I have 32GB of memory) by
cat file_name > /dev/null
Then from a program I access the rows by the key. When I spawn 1000 threads to simultaneously read from the file and monitor the IO using iostat -xkd I see 0 r/s(read requests) but 45 avgqu-sz (average queue size). The 0 r/s makes sense to me since the pages from the file are most likely in the page cache due to the command above. Are the IO requests still queued even if the pages are in the page cache? If only the actual disk reads are queued, how do I explain this phenomenon?