Re: [RFC] User space to kernel space copy optimization
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC] User space to kernel space copy optimization
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC] User space to kernel space copy optimization
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC] User space to kernel space copy optimization
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC] User space to kernel space copy optimization
On Mon, 2015-11-16 at 23:19 +, 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
Re: [RFC] User space to kernel space copy optimization
On Mon, 2015-11-16 at 23:19 +, 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
Re: [RFC] User space to kernel space copy optimization
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Re: [RFC] User space to kernel space copy optimization
On Mon, 2015-11-16 at 21:53 +, 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 majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC] User space to kernel space copy optimization
On Mon, 2015-11-16 at 21:53 +, 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 majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [RFC] User space to kernel space copy optimization
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 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
