Hi
One major reason that Kafka is fast is because it is using sendfile()
for zero copy, as what it described at
https://kafka.apache.org/documentation/#producerconfigs,
This combination of pagecache and sendfile means that on a Kafka
cluster where the consumers are mostly caught up you will see no read
activity on the disks whatsoever as they will be serving data entirely
from cache.
However, when I ran tracing on all my kafka brokers, I didn't get a
single sendfile system call, why his discrepancy?
sudo ./syscount -p 126806 -d 30
Tracing syscalls, printing top 10... Ctrl+C to quit.
[17:44:10]
SYSCALL COUNT
epoll_wait 108482
write 107165
epoll_ctl 95058
futex 86716
read 86388
pread 26910
fstat 9213
getrusage 120
close 27
open 21
