On Wed, 28 Feb 2024 at 21:01, Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx> wrote: [...] > AFAIK the only project using the mm_cid concept I know of today is > tcmalloc. It's very useful to scale data structures such as memory > allocator arenas to the number of concurrently running threads > within a process without having to rely on heuristics on the > user-space side. > > I have plans to migrate LTTng-UST to per-ipc-namespace NUMA-aware > mm_cid as well (after I get around to submit this extension into the > Linux kernel) for user-space ring buffers over shared memory, but my > current focus has been on pushing support for extensible RSEQ into > GNU libc for the past year or so. > > We are getting there though: > > https://sourceware.org/pipermail/libc-alpha/2024-February/154390.html Glad to see this! > Once we have this key piece in place within GNU libc, it will become > easier to extend rseq further because the libc will adapt to the extended > feature set. > > Note that the overhead of the mm_cid assignment within the scheduler > should be negligible after > commit 223baf9d17f2 ("sched: Fix performance regression introduced by mm_cid"). > > Another thing we've actively been working on is to get the "librseq" > project [1] in shape so a copy the librseq headers can be integrated > into the GNU libc project as internal header files. So basically > librseq will become a GNU libc upstream. This will facilitate > implementation of rseq critical section within GNU libc. One of > the possible use-cases will be to move the GNU libc malloc > implementation to per-mm_cid arenas. I suppose if GNU libc malloc starts using it then usage would become ubiquitous in no time. > > I'm aware that TCMalloc was the inspiration for vCPUs [1], then renamed to > > CIDs, but am wondering if other users are out there. > > I'd be curious to learn about those as well. > > I suspect that the lack of official release of librseq critical section > helper headers may contribute to the fact that few applications use advanced > rseq features at this point. I guess you've answered my question, and I conclude "no known open source usage yet". A simple search on Github or the likes also didn't yield anything. I will go and check again in a year or so. ;-) Thanks, -- Marco
