Messages in this thread | | | From | Florian Weimer <> | Subject | Re: [RFC PATCH 1/2] rseq: extend struct rseq with numa node id | Date | Mon, 31 Jan 2022 22:19:09 +0100 |
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* Mathieu Desnoyers:
> Adding the NUMA node id to struct rseq is a straightforward thing to do, > and a good way to figure out if anything in the user-space ecosystem > prevents extending struct rseq. > > This NUMA node id field allows memory allocators such as tcmalloc to > take advantage of fast access to the current NUMA node id to perform > NUMA-aware memory allocation. > > It is also useful for implementing NUMA-aware user-space mutexes.
It can be used to implement getcpu purely in userspace, too. I had plan to hack this together with a node ID cache in TLS, which should offer pretty much the same functionality (except for weird CPU topology changes which alter the node ID of a previously used CPU).
However, I do not understand the need for two fields here. Why isn't one enough?
One field would also avoid the need to mess with rseq_cpu_id_state, maintaining API compatibility.
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