Date: Wed, 9 Dec 2015 03:42:48 +0100
From: Thomas Graf <tgraf@suug.ch>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: David Miller <davem@davemloft.net>, Phil Sutter <phil@nwl.cc>,
        Eric Dumazet <eric.dumazet@gmail.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org, fengguang.wu@intel.com,
        wfg@linux.intel.com, lkp@01.org
Subject: Re: rhashtable: Use __vmalloc with GFP_ATOMIC for table allocation
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On 12/09/15 at 10:38am, Herbert Xu wrote:
> On Wed, Dec 09, 2015 at 03:36:32AM +0100, Thomas Graf wrote:
> > 
> > Without knowing your exact implementation plans: introducing an
> > additional reference indirection for every lookup will have a
> > huge performance penalty as well.
> > 
> > Is your plan to only introduce the master table after an
> > allocation has failed?
> 
> Right, obviously the extra indirections would only come into play
> after a failed allocation.  As soon as we can run the worker thread
> it'll try to remove the extra indirections by doing vmalloc.

OK, this sounds like a good compromise. The penalty is isolated
for the duration of the atomic burst.
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