how much memory does geth need? it eat up all my 8 gb memory then crashed

[johnluan]

System information

Geth version: 1.7.0
OS & Version: Linux 8g ram
Commit hash : (if develop)

Expected behaviour

Geth syncing data normally

Actual behaviour

Geth blow the ram up then crashed.

Steps to reproduce the behaviour

geth --cache=6512 --rpc --rpcaddr=0.0.0.0 --etherbase 0xbaa65ae851612c6a1b10c066cc10c1bfc0b23470 --verbosity=2 --datadir "/data/geth"

Backtrace

Sep 16 09:37:42 10-9-165-200 geth[3391]: fatal error: runtime: out of memory
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime stack:
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.throw(0xf4c0a0, 0x16)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/panic.go:605 +0x95
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.sysMap(0xc5b8d90000, 0x65c00000, 0x0, 0x19303f8)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/mem_linux.go:216 +0x1d0
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.(*mheap).sysAlloc(0x1916b40, 0x65c00000, 0x7fe542057688)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/malloc.go:470 +0xd7
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.(*mheap).grow(0x1916b40, 0x32e00, 0x0)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/mheap.go:887 +0x60
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.(*mheap).allocSpanLocked(0x1916b40, 0x32e00, 0x1930408, 0x7fe543017d38)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/mheap.go:800 +0x334
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.(*mheap).alloc_m(0x1916b40, 0x32e00, 0x7fe567ff0101, 0x41b41c)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/mheap.go:666 +0x118
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.(*mheap).alloc.func1()
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/mheap.go:733 +0x4d
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.systemstack(0x7fe567ffee10)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/asm_amd64.s:360 +0xab
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.(*mheap).alloc(0x1916b40, 0x32e00, 0x7fe567010101, 0x41aa84)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/mheap.go:732 +0xa1
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.largeAlloc(0x65c00000, 0x7fe578bd0101, 0x45dc5b)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/malloc.go:827 +0x98
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.mallocgc.func1()
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/malloc.go:722 +0x46
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.systemstack(0xc4200607b8)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/asm_amd64.s:344 +0x79
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.mstart()
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/proc.go:1125
Sep 16 09:37:42 10-9-165-200 geth[3391]: goroutine 91421 [running]:
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.systemstack_switch()
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/asm_amd64.s:298 fp=0xc51f382be8 sp=0xc51f382be0 pc=0x460870
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.mallocgc(0x65c00000, 0xd95ae0, 0xdeadbe01, 0xc45e8a2240)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/malloc.go:721 +0x7b8 fp=0xc51f382c90 sp=0xc51f382be8 pc=0x417108
Sep 16 09:37:42 10-9-165-200 geth[3391]: runtime.makeslice(0xd95ae0, 0x0, 0x65c00000, 0x7fe578b74000, 0xc525e58000, 0xc470bc1601)
Sep 16 09:37:42 10-9-165-200 geth[3391]: #11/usr/lib/go-1.9/src/runtime/slice.go:54 +0x77 fp=0xc51f382cc0 sp=0xc51f382c90 pc=0x44a037
Sep 16 09:37:42 10-9-165-200 geth[3391]: github.com/ethereum/go-ethereum/vendor/github.com/syndtr/goleveldb/leveldb/memdb.New(0x1815a60, 0xc4201bfcf0, 0x65c00000, 0x0)
Sep 16 09:37:42 10-9-165-200 geth[3391]:

[backtrace]

[fjl]

Using --cache=6512 makes geth use at least 6.5GB of memory. It should not run out of memory if you use a less extreme number for --cache, like 1024. Please also note that larger cache doesn't really speed things up a lot.

[sleimana]

I'm syncing in fast mode, and I'm always ~64 block behind the endBlock. I know it's because of the state tries downloading. The problem is that geth keeps being killed, either by SIGKILL or by Supervisor (exit status 2; expected). Thus, the state tries keep resetting to zero and i'm not able to finish syncing.
How can I prevent geth from being killed, or limit the amount of memory it consumes?
I use Geth [1.8.1-stable] on Ubuntu [16.04]. 3GB RAM. SSD.
geth --syncmode "fast" --cache=1536 --rpc --rpcaddr 127.0.0.1 rpcport=8545 --rpcapi "web3,eth,debug" --maxpeers "128"
thanks
EDIT: I solved this by lowering the cache to 768