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T4240 memory reading bandwidth and memory copy bandwidth are very low, Why?

Question asked by Qinglin Ye on Jan 8, 2018
Latest reply on Jan 9, 2018 by Qinglin Ye

Dear,

We developed a board based on NXP’s QorIQ T4240 CPU and running VxWorks7.0 operating system that booted from U-boot. We tested the memory reading and writing performance of the card and found that the performance of memory read and copy is very low, as follows:

MB/sec T4240 card 1 T4240 card 2 T2080QDS
MemWriteBandwidth8bitSt 371 348 419
MemWriteBandwidth16bitSt 723 667 821
MemWriteBandwidth32bitSt 1375 1291 1572
MemWriteBandwidth64bitSt 2499 2343 2001
MemReadBandwidth8bitSt 233 230 368 ( !!!!!!!!!!! )
MemReadBandwidth16bitSt 338 277 383 ( !!!!!!!!!!! )
MemReadBandwidth32bitSt 438 455 491 ( !!!!!!!!!!! )
MemReadBandwidth64bitSt 513 542 559 ( !!!!!!!!!!! )
MemCopyBandwidth8bitSt 225 208 242 ( !!!!!!!!!!! )
MemCopyBandwidth16bitSt 316 295 321 ( !!!!!!!!!!! )
MemCopyBandwidth32bitSt 344 347 410 ( !!!!!!!!!!! )
MemCopyBandwidth64bitSt 429 384 418 ( !!!!!!!!!!! )
MemcpyBandwidthSt 410 358 406 ( !!!!!!!!!!! )


We think that if 8-bit memory read bandwidth is 230 MB / s, then 16-bit memory read bandwidth is about 460 MB / s. 32 bit memory read bandwidth is about 920 MB/s, 32 bit memory read bandwidth is about 1840 MB / s.

Moreover, low memory read bandwidth directly leads to low memory copy (memcpy and bcopy) bandwidth, which seriously affects the performance of the system.

My questions are:
1) Memory write operations grow at a rate of 2 times , but why is the rate at which memory read or copy is not twice the rate of growth ? Could you tell me why the T4240 CPU has the low read bandwidth and copy bandwidth?
2) Is there any solution?

Please see the attached files for more informations.

Remarks:
1, we used two different manufacturers of T4240 processor boards, which found that the memory read bandwidth and the memory copy bandwidth were very low.
2, we also performed the same test on the T2080QDS board, and found that the memory read bandwidth and the memory copy bandwidth were very low too.
3,Hardware configuration
U-Boot 2015.01+SDKv1.9+geb3d4fc (Oct 14 2017 - 15:31:01)
CPU0: T4240, Version: 2.0, (0x82400020)
Core: e6500, Version: 2.0, (0x80400120)
Clock Configuration:
CPU0:1000 MHz, CPU1:1000 MHz, CPU2:1000 MHz, CPU3:1000 MHz,
CPU4:1000 MHz, CPU5:1000 MHz, CPU6:1000 MHz, CPU7:1000 MHz,
CPU8:1000 MHz, CPU9:1000 MHz, CPU10:1000 MHz, CPU11:1000 MHz,
CCB:700 MHz,
DDR:800 MHz (1600 MT/s data rate) (Asynchronous), IFC:43.750 MHz
FMAN1: 700 MHz
FMAN2: 700 MHz
QMAN: 350 MHz
PME: 333.333 MHz
L1: D-cache 32 KiB enabled
I-cache 32 KiB enabled
Reset Configuration Word (RCW):
00000000: 0e08000a 0a0a0a0a 00000000 00000000
00000010: 04362828 3f55bc00 ec027000 f5000000
00000020: 00100000 00000000 00000000 0001fffc
00000030: 00000100 52800009 00000000 00000028


Thanks you very much !


Ye

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