Why the total memory is 827MB instead of 1GB

Problem

I can only see 846992KB total memory which should be 1023600 KB as i expected.

root@Cubian:/proc# cat meminfo
MemTotal:         846992 kB
MemFree:          729104 kB
Buffers:            5616 kB
Cached:            85140 kB
SwapCached:            0 kB
Active:            24860 kB
Inactive:          77996 kB
Active(anon):      12128 kB
Inactive(anon):     1536 kB
Active(file):      12732 kB
Inactive(file):    76460 kB
Unevictable:           0 kB
Mlocked:               0 kB
HighTotal:        270336 kB
HighFree:         172176 kB
LowTotal:         576656 kB
LowFree:          556928 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:                 0 kB
Writeback:             0 kB
AnonPages:         12172 kB
Mapped:             6412 kB
Shmem:              1568 kB
Slab:               6384 kB
SReclaimable:       1816 kB
SUnreclaim:         4568 kB
KernelStack:        1096 kB
PageTables:          852 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:      423496 kB
Committed_AS:     501032 kB
VmallocTotal:     245760 kB
VmallocUsed:       12200 kB
VmallocChunk:     212928 kB

Solve the problem

Modify uEnv.txt or boot.scr

setenv bootargs console=tty0 console=ttyS0,115200 sunxi_no_mali_mem_reserve sunxi_g2d_mem_reserve=0 sunxi_ve_mem_reserve=0 hdmi.audio=EDID:0 disp.screen0_output_mode=EDID:1280x800p60 root=/dev/mmcblk0p1 rootwait panic=10 consoleblank=0

To compile boot.cmd to boot.scr

mkimage -C none -A arm -T script -d boot.cmd boot.scr

Reference

1. Kernel arguments