netdev - Re: [PATCH iproute2-next] Improve batch times by caching link lookups

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Message-ID: <9f8a0935-2f4c-74e8-038d-61e3b5049f12@gmail.com>
Date:   Mon, 7 Jan 2019 12:57:13 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Ahern <dsahern@...nel.org>, stephen@...workplumber.org
Cc:     netdev@...r.kernel.org, David Ahern <dsahern@...il.com>
Subject: Re: [PATCH iproute2-next] Improve batch times by caching link lookups



On 01/07/2019 12:41 PM, David Ahern wrote:
> From: David Ahern <dsahern@...il.com>
> 
> ip route uses ll_name_to_index to convert the user given device name to an
> index. At the moment ll_name_to_index uses if_nametoindex which is ioctl
> based and does not cache the result. When using a batch file this means
> the same device lookups can be done repeatedly adding unnecessary overhead
> (socket + ioctl call for each device lookup).
> 
> Add a new function, ll_link_get, to send a netlink based RTM_GETLINK. If
> successful, cache the result in idx_head and name_head so future lookups
> can re-use the entry.
> 
> With this change the time to install routes via a batch file is reduced
> from 30.7 seconds to 17.6 seconds (720,022 routes with 2 ecmp nexthops
> where the nexthop device is given).
> 

What time increase if we have 10,000 devices, and install one route ?

Caching 10,000 devices would be quite a waste.