netdev - Re: [PATCH v2 net-next] tcp: md5: use kmalloc() backed scratch areas

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Message-ID: <1467062710.6850.176.camel@edumazet-glaptop3.roam.corp.google.com>
Date:	Mon, 27 Jun 2016 23:25:10 +0200
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Cong Wang <xiyou.wangcong@...il.com>
Cc:	Andy Lutomirski <luto@...capital.net>,
	David Miller <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net-next] tcp: md5: use kmalloc() backed scratch areas

On Mon, 2016-06-27 at 11:31 -0700, Cong Wang wrote:

> Not a problem of your patch, but it seems these allocations never
> get freed once we start using tcp md5. Maybe we should free them
> when the last socket using tcp md5 is gone?

If we constantly allocate-deallocate these tiny blocks for occasional
TCP MD5 use, it becomes quite expensive.

With current code, only first TCP MD5 usage trigger an extra setup cost.