Dear Greg, Thank you for your quick response. Am 26.02.17 um 17:31 schrieb Greg KH: > On Sun, Feb 26, 2017 at 05:29:05PM +0100, Johannes Thoma wrote: >> Dear Kernel hackers, >> >> As far as I understood CMA (contiguous memory allocation) memory is used >> for other purposes as long it isn't requested via cma_alloc() by a >> driver. cma_alloc then tries to free the memory by relocating it and >> returns the contiguous area. >> >> I have a case where cma_alloc() sometimes fails to relocate the memory >> which causes my driver (a GPU driver) to fail starting up (the driver is >> started when the system is running for a while). Is there a way to >> prevent the CM allocator to use the memory for any other purpose? Or >> should I better use another mechanism to allocate contiguous memory at >> boot time (is there a framework for doing so)? > > If at boot time you don't have enough memory, something is really wrong > and your driver shouldn't work, that's to be expected. Try starting it > earlier in the boot process. > Maybe that is the problem. The call to cma_alloc() happens in a driver-specific API function which is called when my application starts (at uptime 30 seconds it always succeeded (at least I didn't observe any failures), however when I restart the application later and call cma_alloc() again (the memory was freed meanwhile) it sometimes fails). > Do you have a pointer to your driver anywhere so we could see if you are > doing something odd with the cma interface? > The driver is part of the imx kernel from boundary devices and can be found here: https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_4.1.15_2.0.0_ga/drivers/mxc/gpu-viv The call to dma_alloc_writecombine (which eventually calls cma_alloc() if I am not completely wrong) can be found in this file: https://github.com/boundarydevices/linux-imx6/blob/boundary-imx_4.1.15_2.0.0_ga/drivers/mxc/gpu-viv/hal/os/linux/kernel/allocator/freescale/gc_hal_kernel_allocator_cma.c Note that I didn't write the driver, I am just using it (it seems to be a port from another OS to Linux to me). As you pointed out the solution would be to allocate the memory earlier in the boot process, by modifying the driver. I will try that in the next few days and let you know the result. Best, - Johannes _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
