virtio-blk: qemu crash after enabling iothreads

[Thomas Barrett]

Hi,

I am experiencing an issue where my qemu virtual machine crashes when:

“cat /proc/<pid>/maps | wc -l” is greater that “cat /proc/sys/vm/max_map_count”

By default, the max_map_count is 65536 on my system. I am not confident that raising this limit will resolve the issue as the number of memory mapped regions appears to slowly increase without bound. 

I have pinned this issue on virtio-block, because the number of mapped memory regions only seems to increase while doing heavy block I/O when IOThreads are enabled. I am using qemu 8.0. 

Does someone have insight on what is causing so many mapped memory regions, whether a maximum exists, and how the maximum scales with vCPUs, queue depth, queue count, and number of IOThreads

Thomas 

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