Re: [PATCH nf-next] netfilter: flowtable: separate replace, destroy and stats to different workqueues

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On 3/24/2021 3:38 AM, Pablo Neira Ayuso wrote:
Hi Marcelo,

On Mon, Mar 22, 2021 at 03:09:51PM -0300, Marcelo Ricardo Leitner wrote:
On Wed, Mar 03, 2021 at 05:11:47PM +0100, Pablo Neira Ayuso wrote:
Or probably make the cookie unique is sufficient? The cookie refers to
the memory address but memory can be recycled very quickly. If the
cookie helps to catch the reorder scenario, then the conntrack id
could be used instead of the memory address as cookie.

Something like this, if I got the idea right, would be even better. If
the entry actually expired before it had a chance of being offloaded,
there is no point in offloading it to then just remove it.

It would be interesting to explore this idea you describe. Maybe a
flag can be set on stale objects, or simply remove the stale object
from the offload queue. So I guess it should be possible to recover
control on the list of pending requests as a batch that is passed
through one single queue_work call.

Removing stale objects is a good optimization for cases when the rate of established connections is greater than the hardware offload insertion rate.
However, with a single workqueue design, a burst of del commands may postpone connection offload tasks.
Postponed offloads may cause additional packets to go through software, thus creating a chain effect which may diminish the system's connection rate.

Marcelo, AFAIU add/del are synchronized by design since the del is triggered by the gc thread.
A del workqueue item will be instantiated only after a connection is in hardware.

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