[Lse-tech] aio performance of

[Helen P. <hp...@us...>]

As I ran async I/O performance test in 2.5.42, I observed little measurable
improvement of response time by using min_nr = nreqs instead of using
min_nr = 1
when calling io_getevents. I observed significant improvement of the cpu
utilization for using specified min_nr = nreqs when calling io_getevents. I
think this is because of reducing number of io_getevents calls when using
min_nr=nreqs.
The following are the results of running async I/O over files.

The SUT is ia32 547 MHz SMP 2-way, 770 MB RAM, 2 SCSI adapters.
The kernel is 2.5.42, and aio library is libaio-0.3.92

Set min_nr = 1 of io_getevents( ) :

Num I/O     ResponseTime      Throughput        CPU         CPU
(nreqs)     (sec)             (MB/sec)          user(%)     sys(%)
10          225.6             730.1             33.2        49.8
20          437.1             749.2             33.2        49.8



Set min_nr = nreqs of io_getevents( ) :

Num I/O     ResponseTime      Throughput        CPU         CPU
(nreqs)     (sec)             (MB/sec)          user(%)     sys(%)
10          220.5             743.1             3.5         46.6
20          434.6             754.0             3.3         46.6

Thanks,
- Helen