netdev - Re: [PATCH net-next 0/3] nfp: flower: speed up stats update loop

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Message-Id: <20181010.223300.2048327590978672766.davem@davemloft.net>
Date:   Wed, 10 Oct 2018 22:33:00 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     jakub.kicinski@...ronome.com
Cc:     netdev@...r.kernel.org, oss-drivers@...ronome.com
Subject: Re: [PATCH net-next 0/3] nfp: flower: speed up stats update loop

From: Jakub Kicinski <jakub.kicinski@...ronome.com>
Date: Mon,  8 Oct 2018 18:57:33 -0700

> This set from Pieter improves performance of processing FW stats
> update notifications.  The FW seems to send those at relatively
> high rate (roughly ten per second per flow), therefore if we want
> to approach the million flows mark we have to be very careful
> about our data structures.
> 
> We tried rhashtable for stat updates, but according to our experiments
> rhashtable lookup on a u32 takes roughly 60ns on an Xeon E5-2670 v3.
> Which translate to a hard limit of 16M lookups per second on this CPU,
> and, according to perf record jhash and memcmp account for 60% of CPU
> usage on the core handling the updates.
> 
> Given that our statistic IDs are already array indices, and considering
> each statistic is only 24B in size, we decided to forego the use
> of hashtables and use a directly indexed array.  The CPU savings are
> considerable.
> 
> With the recent improvements in TC core and with our own bottlenecks
> out of the way Pieter removes the artificial limit of 128 flows, and
> allows the driver to install as many flows as FW supports.

Series applied.