Consequences of changing EigenNonBlockingThreadPool alignment requirements

[leandro-gracia-gil]

Hi,

I'm trying to use ONNXRuntime in a x86 platform that requires TLS sections to have a power of 2 alignment <= 32. I can build the library just fine, but it fails at runtime (when loading it as a shared library) due to this requirement. After investigating a bit it seems that EigenNonBlockingThreadPool is forcing an alignment of 128 "to avoid false sharing with prior fields".

onnxruntime/include/onnxruntime/core/platform/EigenNonBlockingThreadPool.h

Line 193 in 9204cd7

#define ORT_FALSE_SHARING_BYTES 128

I would need to set this alignment down to a maximum of 32 for my particular use case. I can do it locally and there are no build issues, but the comment about false sharing makes me feel uneasy about doing this.

• What is this false sharing about?
• Are there any consequences of this alignment change that I should be aware of, or anything else I should do?

Thanks.

Edit: just to make it clear, I am not asking to make any changes to the github source code. This is for my own local builds.

[leandro-gracia-gil]

@tlh20 Sorry to call you out of the blue. Looks like this is related to this pull of yours. It's a few years old by now, so I'm not sure how much you will remember. But any insights you might have would be appreciated.