Please don't post HTML. On Mon, Jun 27, 2022 at 05:24:10PM +0800, guanghui.fgh wrote: > Thanks. > > 在 2022/6/27 14:34, Mike Rapoport 写道: > > On Sun, Jun 26, 2022 at 07:10:15PM +0800, Guanghui Feng wrote: > > The arm64 can build 2M/1G block/sectiion mapping. When using DMA/DMA32 zone > (enable crashkernel, disable rodata full, disable kfence), the mem_map will > use non block/section mapping(for crashkernel requires to shrink the region > in page granularity). But it will degrade performance when doing larging > continuous mem access in kernel(memcpy/memmove, etc). > > There are many changes and discussions: > commit 031495635b46 > commit 1a8e1cef7603 > commit 8424ecdde7df > commit 0a30c53573b0 > commit 2687275a5843 > > Please include oneline summary of the commit. (See section "Describe your > changes" in Documentation/process/submitting-patches.rst) > > OK, I will add oneline summary in the git commit messages. > > This patch changes mem_map to use block/section mapping with crashkernel. > Firstly, do block/section mapping(normally 2M or 1G) for all avail mem at > mem_map, reserve crashkernel memory. And then walking pagetable to split > block/section mapping to non block/section mapping(normally 4K) [[[only]]] > for crashkernel mem. > > This already happens when ZONE_DMA/ZONE_DMA32 are disabled. Please explain > why is it Ok to change the way the memory is mapped with > ZONE_DMA/ZONE_DMA32 enabled. > > In short: > > 1.building all avail mem with block/section mapping（normally 1G/2M） without > inspecting crashkernel > 2. Reserve crashkernel mem as same as previous doing > 3. only change the crashkernle mem mapping to normal mapping(normally 4k). > With this method, there are block/section mapping as more as possible. This does not answer the question why changing the way the memory is mapped when there is ZONE_DMA/DMA32 and crashkernel won't cause a regression. -- Sincerely yours, Mike.
