netdev - Re: [PATCH bpf-next 00/14] nfp: bpf: add updates, deletes, atomic ops, prandom and packet cache

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Date:   Wed, 28 Mar 2018 19:45:19 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Jakub Kicinski <jakub.kicinski@...ronome.com>
Cc:     daniel@...earbox.net, netdev@...r.kernel.org,
        oss-drivers@...ronome.com, Jan Gossens <jan.gossens@...h-aachen.de>
Subject: Re: [PATCH bpf-next 00/14] nfp: bpf: add updates, deletes, atomic
 ops, prandom and packet cache

On Wed, Mar 28, 2018 at 05:48:24PM -0700, Jakub Kicinski wrote:
> Hi!
> 
> This set adds support for update and delete calls from the datapath,
> as well as XADD instructions (32 and 64 bit) and pseudo random numbers.
> The XADD support depends on verifier enforcing alignment which Daniel
> recently added.  XADD uses NFP's atomic engine which requires values
> to be in big endian, therefore we need to keep track of which parts of
> the values are used as atomics and byte swap them accordingly.  Pseudo
> random numbers are generated using NFP's HW pseudo random number
> generator.
> 
> Jiong tackles initial implementation of packet cache, which he describes
> as follows:
> 
> Memory reads on NFP would first fetch data from memory to transfer-in
> registers, then move them from transfer-in to general registers.
> 
> Given NFP is rich on transfer-in registers, they could serve as memory
> cache.
> 
> This patch tries to identify a sequence of packet data read (BPF_LDX) that
> are executed sequentially, then the total access range of the sequence is
> calculated and attached to each read instruction, the first instruction
> in this sequence is marked with an cache init flag so the execution of
> it would bring in the whole range of packet data for the sequence.
> 
> All later packet reads in this sequence would fetch data from transfer-in
> registers directly, no need to JIT NFP memory access.
> 
> Function call, non-packet-data memory read, packet write and memcpy will
> invalidate the cache and start a new cache range.
> 
> Cache invalidation could be improved in the future, for example packet
> write doesn't need to invalidate the cache if the the write destination
> won't be read again.

Looks exciting.
Applied to bpf-next, thank you Jakub.