[leveldb] InMemoryEnv

[Lucas Lersch]

Hi,

I have noticed that there is an implementation of an In-Memory Environment
in helpers/memenv. Is this supposed to be an alternative to the POSIX
environment, but without durability guarantees?
Is it more like a "prototype" or it is safe to use it?
Finally, what would be the difference between an InMemoryEnv and a POSIX
environment in a tmpfs or ramfs?

Best regards,
Lucas Lersch

['Sanjay Ghemawat' via leveldb]

Post by Lucas Lersch
Hi,
I have noticed that there is an implementation of an In-Memory Environment
in helpers/memenv. Is this supposed to be an alternative to the POSIX
environment, but without durability guarantees?

Yes.

Post by Lucas Lersch
Is it more like a "prototype" or it is safe to use it?

Should be safe. My understanding is that it is used in Chrome/Chromium
(incognito mode?). But I am not 100% sure.

Post by Lucas Lersch
Finally, what would be the difference between an InMemoryEnv and a POSIX
environment in a tmpfs or ramfs?

Some differences I can think of:

(1) tmpfs lifetime is not bound to a process. So a leveldb running against
tmpfs can pick up where it left off after a process restart (assuming
machine hasn't rebooted; tmpfs hasn't been wiped).
(2) My guess is that InMemoryEnv will be a little faster since it requires
no system calls to acces underlying data