Hi all, I'm running the random read test on a 64MB file with 4K block size. The file is small enough to fit in the buffer cache of the system (8 GB DRAM). But default fadvise calls to OS pass two flags (POSIX_FADV_DONTNEED, and POSIX_FADV_RANDOM). With these two settings OS does not try to cache any reads and they all go to the disk. I get ~280 IOPS with 99% disk utilization. And that is fine. But even when I turn fadvise_hint=0, it shows the similar behaviour. Upon further investigation I noticed that irrespective of settings, POSIX_FADV_DONTNEED is always passed to OS (filesetup.c, line 361). Should not it also be restricted when --fadvise_hint is set to zero ? If I don't pass any hint to OS, then after stabilizing whole file is cached in the buffer and IOPS reaches upto 700+K (which I was expecting for small file sizes). Here is the snipped sample output : fio --fadvise_hint=0 --ioengine=psync --direct=0 --rw=randread --bs=4K --size=64M --numjob=1 --runtime=60 --time_based --group_reporting --name=file file: (g=0): rw=randread, bs=4K-4K/4K-4K, ioengine=psync, iodepth=1 fio 1.54 Starting 1 process Jobs: 1 (f=1): [r] [100.0% done] [3043M/0K /s] [761K/0 iops] [eta 00m:00s] file: (groupid=0, jobs=1): err= 0: pid=3820 read : io=121156MB, bw=2019.3MB/s, iops=516931 , runt= 60000msec ...... Disk stats (read/write): sda: ios=7742/82, merge=0/4060, ticks=34608/9112, in_queue=43712, util=32.27% Am I missing something ? cheers, -- Animesh PS ~ I am not on the list so please cc me in the reply. -- To unsubscribe from this list: send the line "unsubscribe fio" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
