tailscale/util
James Tucker 120bfcf1cc util/eventbus: extract non-generic SubscriberFunc constructor body and cache type name
Two changes that share the same intent of reducing per-T duplication
in code that doesn't actually depend on T:

1. Hoist the non-generic portion of newSubscriberFunc[T] into a
   newSubscriberFuncCore() helper. The hoisted work is the time
   timer setup, the subscriberFuncCore allocation, and the
   unregister closure (which captures only the non-generic
   reflect.Type and *subscribeState). The generic body now does
   only the two T-bound things it has to: compute reflect.TypeFor[T]
   and create the dispatch closure.

   Effect on the per-shape-stencil body of newSubscriberFunc[T]:
     before: 523 B per shape (in synthetic test)
     after:  293 B per shape (-230 B per shape; -56% on this body)

2. Cache reflect.Type.String() once at construction (in core.typeName)
   instead of recomputing it every time the dispatch closure runs.
   The dispatch closure also now takes the *subscriberFuncCore directly
   rather than building an intermediate dispatchFuncState struct on
   every call.

   Effect on the dispatch closure body (newSubscriberFunc[T].func1):
     before: 581 B per shape
     after:  480 B per shape (-101 B per shape; -17%)

Combined effect on tailscaled (linux/amd64):
  named-symbol savings via symcost: ~7 KB
  stripped binary delta:            -8 KB (page-quantized)
  arm64 binary delta:                0 (page-quantized)

  cumulative reduction from baseline (5167ff412):
    linux/amd64:  -110,592 bytes (-0.391%)
    linux/arm64:  -131,072 bytes (-0.499%)

Throughput is also improved by the typeName cache: BenchmarkBasic
goes from 2018 ns/op to 1864 ns/op (-7.6%) because the dispatch hot
path no longer allocates a string on every event.

Updates #12614

Change-Id: Ib3a3d6796785e16506330ec034e1144580d467a3
Signed-off-by: James Tucker <james@tailscale.com>
2026-05-12 11:16:04 -07:00
..
backoff all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
bufiox derp,types,util: use bufio Peek+Discard for allocation-free fast reads (#19067) 2026-03-24 10:52:20 -04:00
checkchange all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
cibuild all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
clientmetric all: fix six tests that failed with -count=2 2026-04-13 18:52:57 -07:00
cloudenv all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
cloudinfo all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
cmpver cmd/vet: add subtestnames analyzer; fix all existing violations 2026-04-05 15:52:51 -07:00
codegen all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
ctxkey all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
deephash cmd/vet/lowerell, drive/driveimpl: forbid variables named "l" or "I" 2026-05-04 14:03:28 -07:00
dirwalk all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
dnsname all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
eventbus util/eventbus: extract non-generic SubscriberFunc constructor body and cache type name 2026-05-12 11:16:04 -07:00
execqueue all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
goroutines all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
groupmember all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
hashx all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
httphdr all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
httpm util/httpm: open .git/index to defeat Go test caching 2026-04-15 15:44:19 -07:00
limiter all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
lineiter all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
lineread all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
linuxfw util/linuxfw/linuxfwtest: remove unused package (#19520) 2026-05-04 12:33:12 -07:00
lru all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
mak all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
multierr all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
must all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
nocasemaps all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
osdiag util/osdiag: fix typo in comment (reciever -> receiver) 2026-03-23 12:54:38 +00:00
osshare all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
osuser util/osuser: extend id command fallback for group IDs to freebsd 2026-03-09 08:39:07 +00:00
precompress all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
progresstracking all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
prompt all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
qrcodes all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
quarantine all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
race all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
racebuild all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
rands all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
reload all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
ringlog all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
safediff all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
set all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
singleflight all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
slicesx all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
stringsx all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
syspolicy cmd/vet: add subtestnames analyzer; fix all existing violations 2026-04-05 15:52:51 -07:00
testenv all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
truncate all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
usermetric all: remove AUTHORS file and references to it 2026-01-23 15:49:45 -08:00
vizerror all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00
winutil util/winutil/gp: deflake TestGroupPolicyReadLockClose 2026-05-05 14:02:35 -07:00
zstdframe all: use Go 1.26 things, run most gofix modernizers 2026-03-06 13:32:03 -08:00