meeting: add notes (#3764)

meetings/wasmtime/2022/wasmtime-02-03.md

@@ -2,7 +2,7 @@
 
 **See the [instructions](../README.md) for details on how to attend**
 
-## Agenda
+### Agenda
 1. Opening, welcome and roll call
     1. Note: meeting notes linked in the invite.
     1. Please help add your name to the meeting notes.
@@ -14,8 +14,51 @@
     1. cfallin: update on memfd, CoW, lazy init
     1. _Submit a PR to add your item here_
 
-## Notes
-
 ### Attendees
+- abrown
+- acrichton
+- fitzgen
+- cfallin
+- lgr
+- jlbirch
+- harold
+- sunfish
 
 ### Notes
+
+cfallin: several instantiation performance PRs in the pipeline (or merged):
+ - memfd: anonymous memory file for the heap contents is `mmap`-ed in; can quickly clear any changes in the overlay to reuse it
+ - pooling allocator slot allocation: use the same slot for the module if possible
+ - other changes to instantiation performance: making more things lazy (e.g., `funcref` tables)
+
+cfallin: with the `funcref` tables change, Wasmtime can instantiate the Spidermonkey Wasn module ~3x faster (72us to 22us)
+
+acrichton: could be even faster
+
+jlbirch: in wnat scenarios will we see these benefits?
+
+cfallin: with the memfd changes there are benefits:
+ - when instantiating just once there is no need to do eager init of memory contents (just `mmap`)
+ - caveat: first instantiation might be net same as current implementation...
+ - additional wins if you can reuse the module's slot
+ - table init chnage is a benefit universally
+
+jlbirch: when benchmarking, if we observer inconsistent instantiation times, how can we tell if the fast or slow path is taken?
+
+cfallin: we could expose stats in the affinity allocator
+
+acrichton: note that the module must be the right shape for affinity to work well--dynamic init messes things up (?); this could be improved to recognize more module shapes
+
+abrown: what are some best-case numbers for instantiation?
+
+cfallin: instantiation should be nothing more than an `madvise` call and a few pointer stores
+
+acrichton: for a multi-MB Wasm file, not even pooling, instantiation can be 10us; caveat: single-threadeded result, may find more issues with concurrency
+
+lgr: so this pushes towards doing everything on the fly?
+
+cfallin: yes, majority of work should happen in a new instance--security benefits...
+
+abrown: ittapi crate (for VTune support) has been improved by me, bnjbvr and jlbirch; almost ready for inclusion in the default Wasmtime build--should we support more OS than Linux, macOS, Windows?
+
+acrichton: those are the currently supported OS; that should be fine