Re: [RFC][PATCH 3/3] TCP/IP Critical socket communication mechanism

[Alan Cox]

On Mer, 2005-12-14 at 01:12 -0800, Sridhar Samudrala wrote:
> Pass __GFP_CRITICAL flag with all allocation requests that are critical.
> - All allocations needed to process incoming packets are marked as CRITICAL.
>   This includes the allocations
>      - made by the driver to receive incoming packets
>      - to process and send ARP packets
>      - to create new routes for incoming packets

But your user space that would add the routes is not so protected so I'm
not sure this is actually a solution, more of an extended fudge. In
which case I'm not clear why it is any better than the current
GFP_ATOMIC approach.

> +#define SK_CRIT_ALLOC(sk, flags) ((sk->sk_allocation & __GFP_CRITICAL) | flags)

Lots of hidden conditional logic on critical paths. Also sk should be in
brackets so that the macro evaluation order is defined as should flags

> +#define CRIT_ALLOC(flags) (__GFP_CRITICAL | flags)

Pointless obfuscation


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