| Message ID | 20171005194422.26224-1-robh@kernel.org |
|---|---|
| Headers | show |
| Series | Shrinking DT memory usage | expand |
On Fri, Oct 6, 2017 at 4:30 PM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > On Thu, 5 Oct 2017, Rob Herring wrote: > >> On kernels with a minimal config and a RAM target in the 100s of KB, DT >> is quite a hog of runtime memory usage. How much is dependent on how many >> nodes and properties in the DT which have a corresponding struct device_node >> and struct property in the kernel. Just skipping disabled nodes saves a >> lot by not creating the device_nodes in the first place[1], but there's >> more low hanging fruit by making some of the fields in struct property and >> struct device_node optional. With the changes here, the memory usage goes >> from 17KB to under 8KB on QEMU's ARM virt machine which is a relatively >> small DT. > > My test case went from 118072 bytes ddown to 21548 bytes with this > series. Did that include the changes for FDT skipping status=disabled and to stop storing the full path of every node? With those 2 alone you said it dropped to 25K. > Tested-by: Nicolas Pitre <nico@linaro.org> Thanks. Rob -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Fri, 6 Oct 2017, Rob Herring wrote: > On Fri, Oct 6, 2017 at 4:30 PM, Nicolas Pitre <nicolas.pitre@linaro.org> wrote: > > On Thu, 5 Oct 2017, Rob Herring wrote: > > > >> On kernels with a minimal config and a RAM target in the 100s of KB, DT > >> is quite a hog of runtime memory usage. How much is dependent on how many > >> nodes and properties in the DT which have a corresponding struct device_node > >> and struct property in the kernel. Just skipping disabled nodes saves a > >> lot by not creating the device_nodes in the first place[1], but there's > >> more low hanging fruit by making some of the fields in struct property and > >> struct device_node optional. With the changes here, the memory usage goes > >> from 17KB to under 8KB on QEMU's ARM virt machine which is a relatively > >> small DT. > > > > My test case went from 118072 bytes ddown to 21548 bytes with this > > series. > > Did that include the changes for FDT skipping status=disabled and to > stop storing the full path of every node? With those 2 alone you said > it dropped to 25K. No -- that's with those 6 patches only. Adding the other 2 patches on top and it is down to 11732 bytes. Nicolas -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/05/17 12:44, Rob Herring wrote: > On kernels with a minimal config and a RAM target in the 100s of KB, DT > is quite a hog of runtime memory usage. How much is dependent on how many > nodes and properties in the DT which have a corresponding struct device_node > and struct property in the kernel. Just skipping disabled nodes saves a > lot by not creating the device_nodes in the first place[1], but there's > more low hanging fruit by making some of the fields in struct property and > struct device_node optional. With the changes here, the memory usage goes > from 17KB to under 8KB on QEMU's ARM virt machine which is a relatively > small DT. > > The majority of the diffstat here is just moving all the kobject/sysfs > related code to its own file so we can avoid adding a bunch of ifdefs. > > There's more drastic approaches we could take such as doing the > unflattening at build time and storing the bulk of the unflattened tree > as const data. Grant also has some ideas on storing properties as ids > instead. He's explained it to me, but I still don't understand it. > > Rob > > [1] https://patchwork.kernel.org/patch/9983203/ > > Rob Herring (6): > of: fix missing kobject init for !SYSFS && OF_DYNAMIC config > of: remove struct property.unique_id for FDT > of: make struct property _flags field configurable > of: move kobj_to_device_node() into dynamic.c > of: wrap accesses to device_node kobject > of: make kobject and bin_attribute support configurable > > drivers/base/core.c | 2 +- > drivers/of/Kconfig | 4 ++ > drivers/of/Makefile | 1 + > drivers/of/base.c | 133 --------------------------------------- > drivers/of/dynamic.c | 27 ++------ > drivers/of/kobj.c | 164 ++++++++++++++++++++++++++++++++++++++++++++++++ > drivers/of/of_private.h | 29 +++++++-- > include/linux/of.h | 28 +++++---- > 8 files changed, 215 insertions(+), 173 deletions(-) > create mode 100644 drivers/of/kobj.c > For the entire series: Reviewed-by: Frank Rowand <frowand.list@gmail.com> I don't know if there will be any conflicts between my series "[PATCH 00/12] of: overlay: clean up device tree overlay code" and this series. If you choose to apply this series first, I will make any needed changes to my series. -Frank -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html