From: Willem de Bruijn <willemb@google.com>
To: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Cc: Alex Rosenbaum <alexr@mellanox.com>,
Dave Miller <davem@davemloft.net>,
linux-kernel <linux-kernel@vger.kernel.org>,
netdev@vger.kernel.org,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
Don Skidmore <donald.c.skidmore@intel.com>,
e1000-devel <e1000-devel@lists.sourceforge.net>,
Andi Kleen <andi@firstfloor.org>, HPA <hpa@zytor.com>,
Eliezer Tamir <eliezer@tamir.org.il>
Subject: Re: [PATCH v3 net-next 0/4] net: low latency Ethernet device polling
Date: Tue, 21 May 2013 10:30:53 -0400 [thread overview]
Message-ID: <CA+FuTScYMPUsf0+67FAU0LBfuxhGT8JKyvL1WX=Rjomno75q2A@mail.gmail.com> (raw)
In-Reply-To: <519B68A4.3010406@linux.intel.com>
>> 2. How is the logic aware of RSS and RFS?
>>
>> With TCP sockets, the driver knows the specific ring it need to poll so
>> this should be mapped and provide the best latency.
>
>
> This code is blissfully oblivious of RFS and RSS, it only assumes that the
> packets for a socket are likely to continue to come on the same queue.
> The code is designed to be correct even if you get your data on the wrong
> queue. (your performance will suffer but no more than that.)
>
For low latency, you don't want to have to wait for the IPI that RPS
sets to redirect packets to another CPU. However, this feature works
extremely well with hardware flow steering (nfc/ntuple) and
accelerated RFS, where the device will enqueue directly on an rxqueue
owned exclusively by the destination cpu (if configured correctly).
WARNING: multiple messages have this Message-ID (diff)
From: Willem de Bruijn <willemb@google.com>
To: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Cc: Andi Kleen <andi@firstfloor.org>,
e1000-devel <e1000-devel@lists.sourceforge.net>,
netdev@vger.kernel.org, HPA <hpa@zytor.com>,
Jesse Brandeburg <jesse.brandeburg@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Alex Rosenbaum <alexr@mellanox.com>,
Eliezer Tamir <eliezer@tamir.org.il>,
Dave Miller <davem@davemloft.net>
Subject: Re: [PATCH v3 net-next 0/4] net: low latency Ethernet device polling
Date: Tue, 21 May 2013 10:30:53 -0400 [thread overview]
Message-ID: <CA+FuTScYMPUsf0+67FAU0LBfuxhGT8JKyvL1WX=Rjomno75q2A@mail.gmail.com> (raw)
In-Reply-To: <519B68A4.3010406@linux.intel.com>
>> 2. How is the logic aware of RSS and RFS?
>>
>> With TCP sockets, the driver knows the specific ring it need to poll so
>> this should be mapped and provide the best latency.
>
>
> This code is blissfully oblivious of RFS and RSS, it only assumes that the
> packets for a socket are likely to continue to come on the same queue.
> The code is designed to be correct even if you get your data on the wrong
> queue. (your performance will suffer but no more than that.)
>
For low latency, you don't want to have to wait for the IPI that RPS
sets to redirect packets to another CPU. However, this feature works
extremely well with hardware flow steering (nfc/ntuple) and
accelerated RFS, where the device will enqueue directly on an rxqueue
owned exclusively by the destination cpu (if configured correctly).
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next prev parent reply other threads:[~2013-05-21 14:31 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-05-20 10:15 [PATCH v3 net-next 0/4] net: low latency Ethernet device polling Eliezer Tamir
2013-05-20 10:15 ` Eliezer Tamir
2013-05-20 10:16 ` [PATCH v3 net-next 1/4] net: implement support for low latency socket polling Eliezer Tamir
2013-05-20 10:16 ` Eliezer Tamir
2013-05-20 15:29 ` Eric Dumazet
2013-05-20 19:40 ` David Miller
2013-05-21 7:28 ` Eliezer Tamir
2013-05-21 13:28 ` Eric Dumazet
2013-05-21 17:02 ` Pekka Riikonen
2013-05-21 17:48 ` Eric Dumazet
2013-05-21 17:51 ` Eric Dumazet
2013-05-21 17:51 ` Eric Dumazet
2013-05-21 19:25 ` Eliezer Tamir
2013-05-21 19:25 ` Eliezer Tamir
2013-05-21 19:29 ` Eric Dumazet
2013-05-21 19:29 ` Eric Dumazet
2013-05-21 18:49 ` David Miller
2013-05-21 19:31 ` Pekka Riikonen
2013-05-21 19:31 ` Pekka Riikonen
2013-05-20 10:16 ` [PATCH v3 net-next 2/4] tcp: add TCP support for low latency receive poll Eliezer Tamir
2013-05-20 10:16 ` Eliezer Tamir
2013-05-20 13:49 ` Eric Dumazet
2013-05-20 14:59 ` Eliezer Tamir
2013-05-20 14:59 ` Eliezer Tamir
2013-05-20 10:16 ` [PATCH v3 net-next 3/4] ixgbe: Add support for ndo_ll_poll Eliezer Tamir
2013-05-20 10:16 ` Eliezer Tamir
2013-05-20 20:20 ` Or Gerlitz
2013-05-20 20:20 ` Or Gerlitz
2013-05-20 20:33 ` Andi Kleen
2013-05-20 20:42 ` Or Gerlitz
2013-05-20 21:01 ` Andi Kleen
2013-05-21 6:23 ` Or Gerlitz
2013-05-21 6:23 ` Or Gerlitz
2013-05-21 6:54 ` Eliezer Tamir
2013-05-21 6:54 ` Eliezer Tamir
2013-05-21 7:06 ` Eilon Greenstein
2013-05-21 7:06 ` Eilon Greenstein
2013-05-21 7:14 ` David Miller
2013-05-21 8:24 ` Or Gerlitz
2013-05-21 8:24 ` Or Gerlitz
2013-05-21 8:31 ` Eliezer Tamir
2013-05-21 8:31 ` Eliezer Tamir
2013-05-21 8:39 ` David Miller
2013-05-21 8:42 ` Eliezer Tamir
2013-05-21 8:42 ` Eliezer Tamir
2013-05-21 8:43 ` Or Gerlitz
2013-05-21 8:43 ` Or Gerlitz
2013-05-21 10:27 ` Eliezer Tamir
2013-05-21 10:41 ` Or Gerlitz
2013-05-21 8:21 ` Or Gerlitz
2013-05-21 8:21 ` Or Gerlitz
2013-05-21 8:28 ` Eilon Greenstein
2013-05-21 8:28 ` Eilon Greenstein
2013-05-21 14:19 ` Willem de Bruijn
2013-05-21 14:19 ` Willem de Bruijn
2013-05-20 10:16 ` [PATCH v3 net-next 4/4] ixgbe: add extra stats " Eliezer Tamir
2013-05-20 10:16 ` Eliezer Tamir
2013-05-21 12:06 ` [PATCH v3 net-next 0/4] net: low latency Ethernet device polling Alex Rosenbaum
2013-05-21 12:29 ` Eliezer Tamir
2013-05-21 13:15 ` Alex Rosenbaum
2013-05-21 13:15 ` Alex Rosenbaum
2013-05-21 13:31 ` Eric Dumazet
2013-05-23 11:06 ` Eliezer Tamir
2013-05-23 11:45 ` Alex Rosenbaum
2013-05-21 14:30 ` Willem de Bruijn [this message]
2013-05-21 14:30 ` Willem de Bruijn
2013-05-21 18:15 ` Ben Hutchings
2013-05-21 18:15 ` Ben Hutchings
2013-05-22 9:35 ` Eliezer Tamir
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