3 Replies Latest reply on Feb 2, 2018 6:04 AM by Intel Corporation

    is it possible to exceed limit of bandwidth when using multi-core?


      i'm testing bandwidth using fio benchmark tool. here is my hardware spec

      1. 2 socket per 10cores
      2. Kernel version : 4.8.17
      3. intel SSD 750 series

      cpu : Intel(R) Xeon(R) CPU E5-2650 v3 @ 2.3GHZ ,

      ssd : Intel Solid State Drive 750 series, 400GB, 20nm Intel NAND Flash Memory MLC. NVMe PCIe 3.0*4 ADD-In card.


      I could invalidate the buffer/page cache parts of the files to be used prior to starting I/O when i made the fio file.

      And i used O_DIRECT flag(non-buffered IO) to bypass the page cache and used linux native asynchronous I/O request.

      when i test with one core, fio output says that  bandwidth which core0 received is 1516.7MB/s.

      it doesnt exceed bandwidth limitation of intel SSD 750. it doesn't matter.

      but, when i do this with 3cores, the total bandwidth of cores is exceeds intel SSD 750 bandwidth limitation.

      total amount of bandwidth of 3cores is about 3000MB/s.(core0: 1000mb/s, core1: 1100mb/s, core2: 1000mb/s)

      according to intel SSD 750 spec, it says my intel SSD bandwidth can go up to 2200MB/s. 3000MB/s exceeds 2200MB/s.

      i don't know how this is happened.

      is there somebody help me?