Ok, let me get to another question. Ignore the lstat part of my previous reply as I managed to find the cause.
Now, one thing that is strange for me is the fact that php-fpm is processing image loads as well. Is that not apache's job? (by processing I mean opening the image will call php-fpm to do the job.)
And for each image, it does the following:
getcwd("USER_DIR", 4096) = 49
open("PATH_TO_IMAGE", O_RDONLY) = 7
fstat(7, {st_mode=S_IFREG|0644, st_size=14628, ...}) = 0
lseek(7, 0, SEEK_CUR) = 0
read(7, "GIF89a7\0#\0\367\0\0\0\0\0\277\265\256\244\220\210l+\35\225~g\277\247\232_"..., 8192) = 8192
close(7)
This seems to be very I/O intensive cause it is taking almost the whole CPU time. (with respect to i/o waits)
And since the images are just from a small set of less than 50, can this not be cached or done better? I think php-fpm is not even meant to do this!