From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: Tom Herbert <tom@herbertland.com>
Cc: Haiyang Zhang <haiyangz@microsoft.com>,
David Miller <davem@davemloft.net>,
"vkuznets@redhat.com" <vkuznets@redhat.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
KY Srinivasan <kys@microsoft.com>,
"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"eric.dumazet@gmail.com" <eric.dumazet@gmail.com>
Subject: Re: [PATCH net-next] hv_netvsc: don't make assumptions on struct flow_keys layout
Date: Thu, 14 Jan 2016 17:53:04 +0000 [thread overview]
Message-ID: <20160114175304.161ff0af@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <CALx6S35PbTHF7nY0ugtxCUkc5kUmMYAyuy6ZM34bZ9v42nDudg@mail.gmail.com>
> These results for Toeplitz are not plausible. Given random input you
> cannot expect any hash function to produce such uniform results. I
> suspect either your input data is biased or how your applying the hash
> is.
>
> When I run 64 random IPv4 3-tuples through Toeplitz and Jenkins I get
> something more reasonable:
IPv4 address patterns are not random. Nothing like it. A long long time
ago we did do a bunch of tuning for network hashes using big porn site
data sets. Random it was not.
It's probably hard to repeat that exercise now with geo specific routing,
and all the front end caches and redirectors on big sites but I'd
strongly suggest random input is not a good test, and also that you need
to worry more about hash attacks than perfect distributions.
Alan
WARNING: multiple messages have this Message-ID (diff)
From: One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk>
To: Tom Herbert <tom@herbertland.com>
Cc: "eric.dumazet@gmail.com" <eric.dumazet@gmail.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
Haiyang Zhang <haiyangz@microsoft.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"devel@linuxdriverproject.org" <devel@linuxdriverproject.org>,
David Miller <davem@davemloft.net>
Subject: Re: [PATCH net-next] hv_netvsc: don't make assumptions on struct flow_keys layout
Date: Thu, 14 Jan 2016 17:53:04 +0000 [thread overview]
Message-ID: <20160114175304.161ff0af@lxorguk.ukuu.org.uk> (raw)
In-Reply-To: <CALx6S35PbTHF7nY0ugtxCUkc5kUmMYAyuy6ZM34bZ9v42nDudg@mail.gmail.com>
> These results for Toeplitz are not plausible. Given random input you
> cannot expect any hash function to produce such uniform results. I
> suspect either your input data is biased or how your applying the hash
> is.
>
> When I run 64 random IPv4 3-tuples through Toeplitz and Jenkins I get
> something more reasonable:
IPv4 address patterns are not random. Nothing like it. A long long time
ago we did do a bunch of tuning for network hashes using big porn site
data sets. Random it was not.
It's probably hard to repeat that exercise now with geo specific routing,
and all the front end caches and redirectors on big sites but I'd
strongly suggest random input is not a good test, and also that you need
to worry more about hash attacks than perfect distributions.
Alan
next prev parent reply other threads:[~2016-01-14 17:53 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-07 9:33 [PATCH net-next] hv_netvsc: don't make assumptions on struct flow_keys layout Vitaly Kuznetsov
2016-01-07 9:33 ` Vitaly Kuznetsov
2016-01-07 12:52 ` Eric Dumazet
2016-01-07 13:28 ` Vitaly Kuznetsov
2016-01-07 13:28 ` Vitaly Kuznetsov
2016-01-08 1:02 ` John Fastabend
2016-01-08 3:49 ` KY Srinivasan
2016-01-08 3:49 ` KY Srinivasan
2016-01-08 6:16 ` John Fastabend
2016-01-08 6:16 ` John Fastabend
2016-01-08 18:01 ` KY Srinivasan
2016-01-08 21:07 ` Haiyang Zhang
2016-01-08 21:07 ` Haiyang Zhang
2016-01-09 0:17 ` Tom Herbert
2016-01-09 0:17 ` Tom Herbert
2016-01-10 22:25 ` David Miller
2016-01-10 22:25 ` David Miller
2016-01-13 23:10 ` Haiyang Zhang
2016-01-13 23:10 ` Haiyang Zhang
2016-01-14 4:56 ` David Miller
2016-01-14 4:56 ` David Miller
2016-01-14 17:14 ` Tom Herbert
2016-01-14 17:14 ` Tom Herbert
2016-01-14 17:53 ` One Thousand Gnomes [this message]
2016-01-14 17:53 ` One Thousand Gnomes
2016-01-14 18:24 ` Eric Dumazet
2016-01-14 18:24 ` Eric Dumazet
2016-01-14 18:35 ` Haiyang Zhang
2016-01-14 18:35 ` Haiyang Zhang
2016-01-14 18:48 ` Tom Herbert
2016-01-14 19:15 ` Haiyang Zhang
2016-01-14 19:15 ` Haiyang Zhang
2016-01-14 19:41 ` Tom Herbert
2016-01-14 20:23 ` Haiyang Zhang
2016-01-14 20:23 ` Haiyang Zhang
2016-01-14 21:44 ` Tom Herbert
2016-01-14 21:44 ` Tom Herbert
2016-01-14 22:06 ` David Miller
2016-01-14 22:08 ` Eric Dumazet
2016-01-14 22:08 ` Eric Dumazet
2016-01-14 22:29 ` Haiyang Zhang
2016-01-14 22:29 ` Haiyang Zhang
2016-01-14 17:53 ` Eric Dumazet
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