On 05/02/2018 02:33 PM, Andrew Morton wrote: > On Tue, 1 May 2018 22:58:06 -0700 Prakash Sangappa <prakash.sangappa@xxxxxxxxxx> wrote: >> For analysis purpose it is useful to have numa node information >> corresponding mapped address ranges of the process. Currently >> /proc/<pid>/numa_maps provides list of numa nodes from where pages are >> allocated per VMA of the process. This is not useful if an user needs to >> determine which numa node the mapped pages are allocated from for a >> particular address range. It would have helped if the numa node information >> presented in /proc/<pid>/numa_maps was broken down by VA ranges showing the >> exact numa node from where the pages have been allocated. I'm finding myself a little lost in figuring out what this does. Today, numa_maps might us that a 3-page VMA has 1 page from Node 0 and 2 pages from Node 1. We group *entirely* by VMA: 1000-4000 N0=1 N1=2 We don't want that. We want to tell exactly where each node's memory is despite if they are in the same VMA, like this: 1000-2000 N1=1 2000-3000 N0=1 3000-4000 N1=1 So that no line of output ever has more than one node's memory. It *appears* in this new file as if each contiguous range of memory from a given node has its own VMA. Right? This sounds interesting, but I've never found myself wanting this information a single time that I can recall. I'd love to hear more. Is this for debugging? Are apps actually going to *parse* this file? How hard did you try to share code with numa_maps? Are you sure we can't just replace numa_maps? VMAs are a kernel-internal thing and we never promised to represent them 1:1 in our ABI. Are we going to continue creating new files in /proc every time a tiny new niche pops up? :)
