On Wed, May 3, 2023 at 9:28 AM Steven Rostedt [off-list ref] wrote:

On Wed, 3 May 2023 08:09:28 -0700
Suren Baghdasaryan [off-list ref] wrote:

quoted

There is another issue, which I think can be solved in a smart way but
will either affect performance or would require more memory. With the
tracing approach we don't know beforehand how many individual
allocation sites exist, so we have to allocate code tags (or similar
structures for counting) at runtime vs compile time. We can be smart
about it and allocate in batches or even preallocate more than we need
beforehand but, as I said, it will require some kind of compromise.

This approach is actually quite common, especially since tagging every
instance is usually overkill, as if you trace function calls in a running
kernel, you will find that only a small percentage of the kernel ever
executes. It's possible that you will be allocating a lot of tags that will
never be used. If run time allocation is possible, that is usually the
better approach.

True but the memory overhead should not be prohibitive here. As a
ballpark number, on my machine I see there are 4838 individual
allocation locations and each codetag structure is 32 bytes, so that's
152KB.

-- Steve