It's there any chance to fix it ? dl560g10spmem01:/var/work # /usr/local/bin/fio --filename=/dev/dax0.0 --rw=randrw --refill_buffers --randrepeat=0 --ioengine=mmap --bssplit=4k/4:8k/7:16k/7:32k/15:64k/65:128k/1:256k/1 --rwmixread=5 --iodepth=1 --numjobs=16 --runtime=1800 --group_reporting --name=4-rand-rw-3xx --size=290g 4-rand-rw-3xx: (g=0): rw=randrw, bs=(R) 4096B-256KiB, (W) 4096B-256KiB, (T) 4096B-256KiB, ioengine=mmap, iodepth=1 ... fio-2.99 Starting 16 processes 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 4-rand-rw-3xx: failed to get file size of /dev/dax0.0 -----Original Message----- From: Jens Axboe [mailto:axboe@xxxxxxxxx] Sent: Thursday, November 30, 2017 6:22 AM To: Elliott, Robert (Persistent Memory) <elliott@xxxxxxx>; Gavriliuk, Anton (HPS Ukraine) <anton.gavriliuk@xxxxxxx>; Rebecca Cran <rebecca@xxxxxxxxxxxx>; Sitsofe Wheeler <sitsofe@xxxxxxxxx> Cc: fio@xxxxxxxxxxxxxxx; Kani, Toshimitsu <toshi.kani@xxxxxxx> Subject: Re: fio 3.2 On 11/28/2017 09:13 PM, Elliott, Robert (Persistent Memory) wrote: > small_content_scramble has hardly been touched since 2011, so it > probably hasn't had much performance analysis. That's fair, would be a good thing to look at, especially since it's on by default. > One of the few changes made was to add an integer divide by 1000, > which is always slow (painfully slow on some CPUs): > > offset = ((io_u->start_time.tv_nsec/1000) ^ boffset) & 511; > > perf top doesn't show that taking time - I think the compiler realized > it could pull that calculation out of the loop and just do it once. > Different compilers and compiler options might not realize that. Yeah, int divides suck. This didn't used to be like this, it got added with the nsec conversion. I have fixed this up now. -- Jens Axboe ��.n��������+%������w��{.n�������^n�r������&��z�ޗ�zf���h���~����������_��+v���)ߣ�
