On Thu, Sep 7, 2017 at 11:34 PM, Zvi Effron <zeffron@xxxxxxxxxxxxx> wrote: ... > > I'm not sure entirely how, since I have only just started playing with > this map type, but I suspect a workaround is possible with > BPF_TYPE_ARRAY_OF_MAPS. My suspicion is that you could store the map > you want to replace at index 0 in a pinned array of maps. The XDP > program would load the map out of the array to use it. > > To change the map, have a userspace program load the new map, then set > it as index 0 in the pinned array of maps. The next time the XDP > program runs, it will pull the new map from index 0. > Well, I have to switch between maps based on an "entity switch" in the producing the event. The map type and format is fixed and pinned. Say it could be one per pid, if pid is the entity switch. /sys/bpf/pidno could be the pinned location. Based on the pid at the time of event, I want to consult the map of that pid so I can filter/aggregate/histogram events sent to user space. The "entity switch" could be major:minor:inode, or other such as well (not easy to get from bpf now, but you get the idea). I can't have one or just a few maps because the key value pairs will be different for different entity switches. I might not filter if /sys/pid/pidno map is not present. I guess this is not easy right now because of the way maps are implemented right now, with the verifier doing the magic fixup at the load time. But as BPF usage increases, these kind of use cases will start popping up :) Thanks for your suggestion (Zvi and Daniel). I will explore BPF_TYPE_ARRAY_OF_MAPS if it can fit this case. Thanks, Kiran
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