netdev - Re: [PATCH net-next 0/4] bridge: improve cache utilization

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Date:   Mon, 06 Feb 2017 22:53:35 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     nikolay@...ulusnetworks.com
Cc:     netdev@...r.kernel.org, stephen@...workplumber.org,
        roopa@...ulusnetworks.com, bridge@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 0/4] bridge: improve cache utilization

From: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Date: Sat,  4 Feb 2017 18:05:05 +0100

> This is the first set which begins to deal with the bad bridge cache
> access patterns. The first patch rearranges the bridge and port structs
> a little so the frequently (and closely) accessed members are in the same
> cache line. The second patch then moves the garbage collection to a
> workqueue trying to improve system responsiveness under load (many fdbs)
> and more importantly removes the need to check if the matched entry is
> expired in __br_fdb_get which was a major source of false-sharing.
> The third patch is a preparation for the final one which
> If properly configured, i.e. ports bound to CPUs (thus updating "updated"
> locally) then the bridge's HitM goes from 100% to 0%, but even without
> binding we get a win because previously every lookup that iterated over
> the hash chain caused false-sharing due to the first cache line being
> used for both mac/vid and used/updated fields.
> 
> Some results from tests I've run:
> (note that these were run in good conditions for the baseline, everything
>  ran on a single NUMA node and there were only 3 fdbs)
> 
> 1. baseline
> 100% Load HitM on the fdbs (between everyone who has done lookups and hit
>                             one of the 3 hash chains of the communicating
>                             src/dst fdbs)
> Overall 5.06% Load HitM for the bridge, first place in the list
> 
> 2. patched & ports bound to CPUs
> 0% Local load HitM, bridge is not even in the c2c report list
> Also there's 3% consistent improvement in netperf tests.

Looks great, series applied, thanks!