In Advanced Programming in Unix Environment 3th, 3.9, I/O Efficiency, I read about this:
The file was read using the program shown in Figure 3.5, with standard output redirected to /dev/null. The file system used for this test was the Linux ext4 file system with 4,096-byte blocks. (The st_blksize value, which we describe in Section 4.12, is 4,096.) This accounts for the minimum in the system time occurring at the few timing measurements starting around a BUFFSIZE of 4,096. Increasing the buffer size beyond this limit has little positive effect.
My question is why "Increasing the buffer size beyond this limit has little positive effect"? I think increasing the buffer size will definitely reduce the user cpu time and system cpu time because of the reduce of number of loops so that the clock time will also be reduced to certain degrees, Isn't that so? And why?