Bear in mind a separate process doesn't buy you anything without a sandbox,
and those are expensive (in terms of complexity).
On 21 Feb 2014 11:40, "Jeff Garzik" <jgarzik@bitpay.com> wrote:

> [Meta: "Bitcoin Core" is the newfangled branding of bitcoind /
> Bitcoin-Qt reference implementation, in case you wondering.]
>
> Several sites, including BitPay, use bitcoind outside the standard
> role of wallet software.  bitcoind can be used purely for payment
> network access and management.  I call this the "border router" role.
> Upcoming version 0.9 will feature the ability to disable the bitcoind
> wallet at compile time or runtime. This permits a more optimized
> border router profile, reducing process size by 40-200MB according to
> some reports.
>
> Recent IRC discussion have floated a rough proposal for a wallet
> next-step:  Running the Bitcoin Core wallet as a separate process, a
> separate binary, from the blockchain engine.  The wallet process would
> communicate with the blockchain engine using existing RPC and P2P
> channels, becoming a real SPV client.  This accomplishes a
> longstanding security goal of sandboxing away wallet keys and
> sensitive data from the network-exposed P2P engine, in a separate
> process, among other benefits.
>
> Simple forking was explored a bit.  I did some hacking in that
> direction, as it seemed potentially lightweight and somewhat easy to
> me: https://github.com/jgarzik/bitcoin/tree/fork  fork+pipe is fine
> for Linux and OSX/BSD.  However, Windows requires an exec-like
> solution to create a new process.  MSDN does give us a Unix-pipe-like
> solution:
> http://msdn.microsoft.com/en-us/library/edze9h7e%28v=vs.80%29.aspx
>  Others pointed to boost interprocess communication APIs, which come
> with their own set of caveats.  Such a solution would involve a brand
> new IPC protocol, and lots of brand new glue code.
>
> Separate programs seems better.  Windows forces us to achieve process
> separation via exec-like method.  We already have IPC: RPC + P2P.
> Modern OS's make localhost sockets just about as fast as other IPCs
> methods.  Linux, at least, employs zero-copy for localhost sockets in
> many situations, similar to the kernel's pipe tricks.
>
> Pieter has been working on headers-first sync:
> https://github.com/bitcoin/bitcoin/pull/2964  Moving along this
> wallet/blockchain engine split requires upping the review&test
> bandwidth on Pieter's PRs, such as
> https://github.com/bitcoin/bitcoin/pull/3514
>
> Unsure how much of the separate-binary discussion Gavin saw, so cc'd
> for emphasis.
>
> --
> Jeff Garzik
> Bitcoin core developer and open source evangelist
> BitPay, Inc.      https://bitpay.com/
>
>
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