Re: Contiguous Memory Allocator (CMA)
Hello Fabio, I haven't done it because I haven't had time and CONFIG_DMA_CMA has not been enabled in the kernel I was fooling with. Yes I do know how to build the kernel. Thanks for all the help. Once I get it working I'll let you know. Cheerio S On Sat, Jan 8, 2022, 17:14 FMDF wrote: > On Sat, 8 Jan 2022, 14:37 Sadanand Warrier, > wrote: > >> Hello Fabio >>Thanks for the response. I had already accessed that link that you >> have pasted. Michal Nazarewicz also has a few other points on using >> CMA. >> When I tried to use the API after setting cma=128M on the kernel boot >> command line and booted the kernel, the api returned without >> allocating memory >> when the driver was installed. >> The dmesg shows that 128M was reserved for CMA but dma_alloc_coherent >> failed. >> It seems that default CentOS and perhaps Ubuntu kernels are not >> compiled with CONFIG_DMA_CMA=yes for the dma_alloc_coherent to work. >> I'm not sure if this is a valid assumption. I haven't tried >> recompiling the kernel yet with that option set. >> From what I have managed to eke out we need CONFIG_CMA=yes and >> CONFIG_DMA_CMA=yes too. >> > > If I recall it well, I think they are needed. Why haven't you yet checked? > > I assume that you know how to change your .config, re-build the kernel and > the modules and install everything in the right places. Don't you? > >> > Just grep the ".config" of your distro. It should be placed in /boot/ > with a name like "config-`uname -r`" or in /usr/src/linux/ with its true > name (.config) and see if those options are enabled. Or you may use > directly "make menuconfig" and search with its special keys. Then "make -jN > && sudo make modules_install install" (and hope that installkernel is not > broken like it has been in openSUSE Tumbleweed for weeks). :( > > I'm not an expert about this particular subject, so if they have already > been enabled I cannot help you with more than the above information. That > article in lwn.net is everything I've studied about this subject and I > haven't ever used it in kernel programming. > > Regards, > > Fabio M. De Francesco > > >> Thanks >> S >> >> >> On Sat, 8 Jan 2022 at 07:23, FMDF wrote: >> > >> > On Tue, 21 Dec 2021, 15:36 Sadanand Warrier, >> wrote: >> >> >> >> Hello >> >> Is CMA still supported as described in this document >> >> https://lwn.net/Articles/396707/ ? >> > >> > >> > Yes, it is. >> > >> > Read the following instructions on how to use that feature: >> > >> > "A deep dive into CMA" at >> > https://lwn.net/Articles/486301/ >> > >> > Regards, >> > >> > Fabio M. De Francesco >> > >> > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Contiguous Memory Allocator (CMA)
On Sat, 8 Jan 2022, 14:37 Sadanand Warrier, wrote: > Hello Fabio >Thanks for the response. I had already accessed that link that you > have pasted. Michal Nazarewicz also has a few other points on using > CMA. > When I tried to use the API after setting cma=128M on the kernel boot > command line and booted the kernel, the api returned without > allocating memory > when the driver was installed. > The dmesg shows that 128M was reserved for CMA but dma_alloc_coherent > failed. > It seems that default CentOS and perhaps Ubuntu kernels are not > compiled with CONFIG_DMA_CMA=yes for the dma_alloc_coherent to work. > I'm not sure if this is a valid assumption. I haven't tried > recompiling the kernel yet with that option set. > From what I have managed to eke out we need CONFIG_CMA=yes and > CONFIG_DMA_CMA=yes too. > If I recall it well, I think they are needed. Why haven't you yet checked? I assume that you know how to change your .config, re-build the kernel and the modules and install everything in the right places. Don't you? > Just grep the ".config" of your distro. It should be placed in /boot/ with a name like "config-`uname -r`" or in /usr/src/linux/ with its true name (.config) and see if those options are enabled. Or you may use directly "make menuconfig" and search with its special keys. Then "make -jN && sudo make modules_install install" (and hope that installkernel is not broken like it has been in openSUSE Tumbleweed for weeks). :( I'm not an expert about this particular subject, so if they have already been enabled I cannot help you with more than the above information. That article in lwn.net is everything I've studied about this subject and I haven't ever used it in kernel programming. Regards, Fabio M. De Francesco > Thanks > S > > > On Sat, 8 Jan 2022 at 07:23, FMDF wrote: > > > > On Tue, 21 Dec 2021, 15:36 Sadanand Warrier, > wrote: > >> > >> Hello > >> Is CMA still supported as described in this document > >> https://lwn.net/Articles/396707/ ? > > > > > > Yes, it is. > > > > Read the following instructions on how to use that feature: > > > > "A deep dive into CMA" at > > https://lwn.net/Articles/486301/ > > > > Regards, > > > > Fabio M. De Francesco > > > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Contiguous Memory Allocator (CMA)
Hello Fabio Thanks for the response. I had already accessed that link that you have pasted. Michal Nazarewicz also has a few other points on using CMA. When I tried to use the API after setting cma=128M on the kernel boot command line and booted the kernel, the api returned without allocating memory when the driver was installed. The dmesg shows that 128M was reserved for CMA but dma_alloc_coherent failed. It seems that default CentOS and perhaps Ubuntu kernels are not compiled with CONFIG_DMA_CMA=yes for the dma_alloc_coherent to work. I'm not sure if this is a valid assumption. I haven't tried recompiling the kernel yet with that option set. >From what I have managed to eke out we need CONFIG_CMA=yes and CONFIG_DMA_CMA=yes too. Thanks S On Sat, 8 Jan 2022 at 07:23, FMDF wrote: > > On Tue, 21 Dec 2021, 15:36 Sadanand Warrier, > wrote: >> >> Hello >> Is CMA still supported as described in this document >> https://lwn.net/Articles/396707/ ? > > > Yes, it is. > > Read the following instructions on how to use that feature: > > "A deep dive into CMA" at > https://lwn.net/Articles/486301/ > > Regards, > > Fabio M. De Francesco > ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Contiguous Memory Allocator (CMA)
On Tue, 21 Dec 2021, 15:36 Sadanand Warrier, wrote: > Hello > Is CMA still supported as described in this document > https://lwn.net/Articles/396707/ ? > Yes, it is. Read the following instructions on how to use that feature: "A deep dive into CMA" at https://lwn.net/Articles/486301/ Regards, Fabio M. De Francesco ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Contiguous Memory Allocator (CMA)
Hello Is CMA still supported as described in this document https://lwn.net/Articles/396707/ ? Or has it changed and there is a newer version which details how to allocate a chunk of contiguous memory on bootup and then use it with a loadable kernel module? What I want to do is allocate a chunk of contiguous memory at boot time and use it with a loadable driver. It will be a vanilla Centos kernel and I wonder if they are compiled with the CMA enabled. When I check dmesg I see " 0K cma-reserved" so it still exists. Thanks S ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Re: Contiguous memory allocator
cma_declare_contiguous() allocates memory from memblock. cma_init_reserved_mem() initialize the memory. Then the memory is given to buddy allocator with migration type MIGRATE_MOVABLE. when CMA needs thosepages, it can take it from buddy allocator. We are supposed to use equivalent DMA api dma_declare_contiguous(). dma_declare_contiguous() calls cma_declare_contiguous(). http://lxr.free-electrons.com/source/arch/arm/mach-davinci/devices-da8xx.c#L833 Regards Manoj Nayak ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
Contiguous memory allocator
What is the difference between function cma_init_reserved_mem() and cma_declare_contiguous()? If I am trying to allocate new CMA area at boot time, How to do that? regards, Ronit ___ Kernelnewbies mailing list Kernelnewbies@kernelnewbies.org http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
