netdev - Re: [patch net] mlxsw: spectrum_router: Avoid expensive lookup during route removal

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Date:   Sun, 08 Oct 2017 10:06:19 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jiri@...nulli.us
Cc:     netdev@...r.kernel.org, idosch@...lanox.com, mlxsw@...lanox.com,
        dsa@...ulusnetworks.com
Subject: Re: [patch net] mlxsw: spectrum_router: Avoid expensive lookup
 during route removal

From: Jiri Pirko <jiri@...nulli.us>
Date: Sun,  8 Oct 2017 11:53:26 +0200

> From: Ido Schimmel <idosch@...lanox.com>
> 
> In commit fc922bb0dd94 ("mlxsw: spectrum_router: Use one LPM tree for
> all virtual routers") I increased the scale of supported VRFs by having
> all of them share the same LPM tree.
> 
> In order to avoid look-ups for prefix lengths that don't exist, each
> route removal would trigger an aggregation across all the active virtual
> routers to see which prefix lengths are in use and which aren't and
> structure the tree accordingly.
> 
> With the way the data structures are currently laid out, this is a very
> expensive operation. When preformed repeatedly - due to the invocation
> of the abort mechanism - and with enough VRFs, this can result in a hung
> task.
> 
> For now, avoid this optimization until it can be properly re-added in
> net-next.
> 
> Fixes: fc922bb0dd94 ("mlxsw: spectrum_router: Use one LPM tree for all virtual routers")
> Signed-off-by: Ido Schimmel <idosch@...lanox.com>
> Reported-by: David Ahern <dsa@...ulusnetworks.com>
> Tested-by: David Ahern <dsa@...ulusnetworks.com>
> Signed-off-by: Jiri Pirko <jiri@...lanox.com>

Applied.