linux-kernel - Re: [PATCH RFC net-next] net: epoll support for busy poll

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Message-ID: <1377093188.4226.108.camel@edumazet-glaptop>
Date:	Wed, 21 Aug 2013 06:53:08 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, e1000-devel@...ts.sourceforge.net,
	Eilon Greenstein <eilong@...adcom.com>,
	Amir Vadai <amirv@...lanox.com>,
	Willem de Bruijn <willemb@...gle.com>,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH RFC net-next] net: epoll support for busy poll

On Wed, 2013-08-21 at 13:39 +0300, Eliezer Tamir wrote:

> 
> Instead of remembering the napi_id for all the sockets in an epoll,
> we only track the first socket we see with any unique napi_id.
> The rational for this is that while there may be many thousands of
> sockets tracked by a single epoll, we expect to only see a handful
> of unique napi_ids in most cases.

This looks buggy assumption to me.

We use epoll() with in the order of millions of fds per epoller, and
typically one napi_id per cpu.

With your model, we would have to use nr_cpu epollers and make sure that
sockets are properly placed on those epollers by their napi_ids.



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