* [RFC] User space to kernel space copy optimization
@ 2015-11-16 21:53 Sinan Kaya
2015-11-16 22:57 ` Jiang, Dave
2015-12-05 8:10 ` Vinod Koul
0 siblings, 2 replies; 6+ messages in thread
From: Sinan Kaya @ 2015-11-16 21:53 UTC (permalink / raw)
To: linux-arm-kernel
One of the things I'm interested in is to use a memcpy capable DMA
engine HW to optimize user space and kernel space parameter copying.
Of course, this will not be viable for all parameter sizes but I can see
this being useful. The goal is to save power in the cost of little
performance.
Before I go and invent my own mechanism, I'd like to have ideas on what
an acceptable solution would look like. Especially, I'm looking for a
generic implementation that could plug into any DMA engine HW.
--
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC] User space to kernel space copy optimization
2015-11-16 21:53 [RFC] User space to kernel space copy optimization Sinan Kaya
@ 2015-11-16 22:57 ` Jiang, Dave
2015-11-16 23:19 ` Sinan Kaya
2015-12-05 8:10 ` Vinod Koul
1 sibling, 1 reply; 6+ messages in thread
From: Jiang, Dave @ 2015-11-16 22:57 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, 2015-11-16 at 21:53 +0000, Sinan Kaya wrote:
> One of the things I'm interested in is to use a memcpy capable DMA
> engine HW to optimize user space and kernel space parameter copying.
Have you looked at why NET_DMA was deprecated and using DMA engine to
do kernel->user copy could be a problem?
https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/
?id=77873803363c
>
> Of course, this will not be viable for all parameter sizes but I can
> see
> this being useful. The goal is to save power in the cost of little
> performance.
>
> Before I go and invent my own mechanism, I'd like to have ideas on
> what
> an acceptable solution would look like. Especially, I'm looking for a
> generic implementation that could plug into any DMA engine HW.
>
> --
> Sinan Kaya
> Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center,
> Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
> Linux Foundation Collaborative Project
> --
> To unsubscribe from this list: send the line "unsubscribe dmaengine"
> in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC] User space to kernel space copy optimization
2015-11-16 22:57 ` Jiang, Dave
@ 2015-11-16 23:19 ` Sinan Kaya
2015-11-17 19:28 ` Jiang, Dave
0 siblings, 1 reply; 6+ messages in thread
From: Sinan Kaya @ 2015-11-16 23:19 UTC (permalink / raw)
To: linux-arm-kernel
On 11/16/2015 5:57 PM, Jiang, Dave wrote:
>> One of the things I'm interested in is to use a memcpy capable DMA
>> > engine HW to optimize user space and kernel space parameter copying.
> Have you looked at why NET_DMA was deprecated and using DMA engine to
> do kernel->user copy could be a problem?
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/
> ?id=77873803363c
>
As far as I know, the problem was the TCP/IP stack trying to work on a
buffer that was given to the DMA engine for moving. It was causing stale
data problems.
The goal was to let DMA engine move the data while TCP/IP stack was
working on something else. Then, synchronize on a known point. Of
course, when above violation happens; things break.
Are you expecting a similar problem on user space to kernel space
interaction? I think the ownership buffers are pretty much defined,
isn't it?
--
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC] User space to kernel space copy optimization
2015-11-16 23:19 ` Sinan Kaya
@ 2015-11-17 19:28 ` Jiang, Dave
0 siblings, 0 replies; 6+ messages in thread
From: Jiang, Dave @ 2015-11-17 19:28 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, 2015-11-16 at 23:19 +0000, Sinan Kaya wrote:
> On 11/16/2015 5:57 PM, Jiang, Dave wrote:
> > > One of the things I'm interested in is to use a memcpy capable
> > > DMA
> > > > engine HW to optimize user space and kernel space parameter
> > > > copying.
> > Have you looked at why NET_DMA was deprecated and using DMA engine
> > to
> > do kernel->user copy could be a problem?
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/com
> > mit/
> > ?id=77873803363c
> >
>
> As far as I know, the problem was the TCP/IP stack trying to work on
> a
> buffer that was given to the DMA engine for moving. It was causing
> stale
> data problems.
>
> The goal was to let DMA engine move the data while TCP/IP stack was
> working on something else. Then, synchronize on a known point. Of
> course, when above violation happens; things break.
>
> Are you expecting a similar problem on user space to kernel space
> interaction? I think the ownership buffers are pretty much defined,
> isn't it?
No. I thought you were investigating both ways so thought you might
need to be aware.
>
>
> --
> Sinan Kaya
> Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center,
> Inc.
> Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
> Linux Foundation Collaborative Project
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC] User space to kernel space copy optimization
2015-11-16 21:53 [RFC] User space to kernel space copy optimization Sinan Kaya
2015-11-16 22:57 ` Jiang, Dave
@ 2015-12-05 8:10 ` Vinod Koul
2015-12-06 4:24 ` Sinan Kaya
1 sibling, 1 reply; 6+ messages in thread
From: Vinod Koul @ 2015-12-05 8:10 UTC (permalink / raw)
To: linux-arm-kernel
On Mon, Nov 16, 2015 at 04:53:27PM -0500, Sinan Kaya wrote:
> One of the things I'm interested in is to use a memcpy capable DMA
> engine HW to optimize user space and kernel space parameter copying.
>
> Of course, this will not be viable for all parameter sizes but I can see
> this being useful. The goal is to save power in the cost of little
> performance.
>
> Before I go and invent my own mechanism, I'd like to have ideas on what
> an acceptable solution would look like. Especially, I'm looking for a
> generic implementation that could plug into any DMA engine HW.
Do you have a proposal on how this generic solution should look like, broad
contours of the design to start off with and we can start from that point
--
~Vinod
^ permalink raw reply [flat|nested] 6+ messages in thread
* [RFC] User space to kernel space copy optimization
2015-12-05 8:10 ` Vinod Koul
@ 2015-12-06 4:24 ` Sinan Kaya
0 siblings, 0 replies; 6+ messages in thread
From: Sinan Kaya @ 2015-12-06 4:24 UTC (permalink / raw)
To: linux-arm-kernel
On 12/5/2015 3:10 AM, Vinod Koul wrote:
> On Mon, Nov 16, 2015 at 04:53:27PM -0500, Sinan Kaya wrote:
>> One of the things I'm interested in is to use a memcpy capable DMA
>> engine HW to optimize user space and kernel space parameter copying.
>>
>> Of course, this will not be viable for all parameter sizes but I can see
>> this being useful. The goal is to save power in the cost of little
>> performance.
>>
>> Before I go and invent my own mechanism, I'd like to have ideas on what
>> an acceptable solution would look like. Especially, I'm looking for a
>> generic implementation that could plug into any DMA engine HW.
>
> Do you have a proposal on how this generic solution should look like, broad
> contours of the design to start off with and we can start from that point
>
No, not yet. AFAIK, some of these optimization ideas have been tried by
the Intel IO/AT in the past (kernel 2.6) and were rejected by the
upstream. I wanted to see if anybody had better ideas these days that is
upstream friendly.
--
Sinan Kaya
Qualcomm Technologies, Inc. on behalf of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a
Linux Foundation Collaborative Project
^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2015-12-06 4:24 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2015-11-16 21:53 [RFC] User space to kernel space copy optimization Sinan Kaya
2015-11-16 22:57 ` Jiang, Dave
2015-11-16 23:19 ` Sinan Kaya
2015-11-17 19:28 ` Jiang, Dave
2015-12-05 8:10 ` Vinod Koul
2015-12-06 4:24 ` Sinan Kaya
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).