netdev - Re: [PATCH 2/7] net-tcp: Fast Open client

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Message-Id: <20120716.231535.1001789192358609710.davem@davemloft.net>
Date:	Mon, 16 Jul 2012 23:15:35 -0700 (PDT)
From:	David Miller <davem@...emloft.net>
To:	ycheng@...gle.com
Cc:	hkchu@...gle.com, edumazet@...gle.com, ncardwell@...gle.com,
	sivasankar@...ucsd.edu, netdev@...r.kernel.org
Subject: Re: [PATCH 2/7] net-tcp: Fast Open client - cookie cache

From: Yuchung Cheng <ycheng@...gle.com>
Date: Mon, 16 Jul 2012 14:16:45 -0700

> The Fast Open cookie cache is used by a TCP Fast Open client to store
> remote servers' Fast Open cookies. It stores one Fast Open cookie
> per IP (v4 or v6) and by default 1024 cookies total. The size is
> tunable via /proc/sys/net/ipv4/tcp_fastopen_cookies. Setting it to 0
> will flush the cache.
> 
> The inetpeer cache also caches remote peer's information but the
> in-active cache entries are recycled on the scale of minutes. Therefore
> a separate storage is required but the lookup is done via inetpeer.
> Each inetpeer entry holds a cookie cache entry pointer (if TFO is used
> on that IP). On cache write, the cookie cache entry is allocated and
> stored in a list for LRU replacement. A spinlock protects any R/W
> operation on the cookie cache entry and the list.
> 
> Signed-off-by: Yuchung Cheng <ycheng@...gle.com>

I would store these in the new tcp metrics cache.

Any argument against doing so wrt. expiry is bogus, because you can
implement whatever time limit you want using a jiffies based
expiration value.
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