Refactor rate_limit.go for more clarify
This wasn't intended to change the behavior, but it does slightly.
Previously any requests to acquire memory wouldn't block; only
(subsequent) requests for execution would block (if another
caller had already consumed the memory quota). Now the requests
for memory can also also block.
It turns out in a brief test on my computer that soong_zip
runs about 10 to 20% faster with this change than without it.
The final step involving soong_zip decreased from about
3.6 sec to about 3.3 sec in tests on my computer.
When testing the process of re-zipping the contents of
angler-target_files*.zip , the time decreased from about
6.3 sec to about 5.3 sec in tests on my computer, and the
peak memory usage reported by `top` decreased from about
1.5g to 1g
Bug: 64536066
Test: m -j dist showcommands # which runs soong_zip to package everything
Change-Id: I0422e4c363c675bb7a93309fac4616c768bfbe8f
diff --git a/cmd/soong_zip/rate_limit.go b/cmd/soong_zip/rate_limit.go
index 9e95bc1..04102b7 100644
--- a/cmd/soong_zip/rate_limit.go
+++ b/cmd/soong_zip/rate_limit.go
@@ -15,71 +15,54 @@
package main
import (
+ "fmt"
"runtime"
)
type RateLimit struct {
- requests chan struct{}
- finished chan int
- released chan int
- stop chan struct{}
+ requests chan request
+ completions chan int64
+
+ stop chan struct{}
}
-// NewRateLimit starts a new rate limiter with maxExecs number of executions
-// allowed to happen at a time. If maxExecs is <= 0, it will default to the
-// number of logical CPUs on the system.
-//
-// With Finish and Release, we'll keep track of outstanding buffer sizes to be
-// written. If that size goes above maxMem, we'll prevent starting new
-// executions.
-//
-// The total memory use may be higher due to current executions. This just
-// prevents runaway memory use due to slower writes.
-func NewRateLimit(maxExecs int, maxMem int64) *RateLimit {
- if maxExecs <= 0 {
- maxExecs = runtime.NumCPU()
- }
- if maxMem <= 0 {
- // Default to 512MB
- maxMem = 512 * 1024 * 1024
- }
+type request struct {
+ size int64
+ serviced chan struct{}
+}
+// NewRateLimit starts a new rate limiter that permits the usage of up to <capacity> at once,
+// except when no capacity is in use, in which case the first caller is always permitted
+func NewRateLimit(capacity int64) *RateLimit {
ret := &RateLimit{
- requests: make(chan struct{}),
+ requests: make(chan request),
+ completions: make(chan int64),
- // Let all of the pending executions to mark themselves as finished,
- // even if our goroutine isn't processing input.
- finished: make(chan int, maxExecs),
-
- released: make(chan int),
- stop: make(chan struct{}),
+ stop: make(chan struct{}),
}
- go ret.goFunc(maxExecs, maxMem)
+ go ret.monitorChannels(capacity)
return ret
}
-// RequestExecution blocks until another execution can be allowed to run.
-func (r *RateLimit) RequestExecution() Execution {
- <-r.requests
- return r.finished
+// RequestExecution blocks until another execution of size <size> can be allowed to run.
+func (r *RateLimit) Request(size int64) {
+ request := request{
+ size: size,
+ serviced: make(chan struct{}, 1),
+ }
+
+ // wait for the request to be received
+ r.requests <- request
+
+ // wait for the request to be accepted
+ <-request.serviced
}
-type Execution chan<- int
-
-// Finish will mark your execution as finished, and allow another request to be
-// approved.
-//
-// bufferSize may be specified to count memory buffer sizes, and must be
-// matched with calls to RateLimit.Release to mark the buffers as released.
-func (e Execution) Finish(bufferSize int) {
- e <- bufferSize
-}
-
-// Call Release when finished with a buffer recorded with Finish.
-func (r *RateLimit) Release(bufferSize int) {
- r.released <- bufferSize
+// Finish declares the completion of an execution of size <size>
+func (r *RateLimit) Finish(size int64) {
+ r.completions <- size
}
// Stop the background goroutine
@@ -87,29 +70,83 @@
close(r.stop)
}
-func (r *RateLimit) goFunc(maxExecs int, maxMem int64) {
- var curExecs int
- var curMemory int64
+// monitorChannels processes incoming requests from channels
+func (r *RateLimit) monitorChannels(capacity int64) {
+ var usedCapacity int64
+ var currentRequest *request
for {
- var requests chan struct{}
- if curExecs < maxExecs && curMemory < maxMem {
+ var requests chan request
+ if currentRequest == nil {
+ // If we don't already have a queued request, then we should check for a new request
requests = r.requests
}
select {
- case requests <- struct{}{}:
- curExecs++
- case amount := <-r.finished:
- curExecs--
- curMemory += int64(amount)
- if curExecs < 0 {
- panic("curExecs < 0")
+ case newRequest := <-requests:
+ currentRequest = &newRequest
+ break
+ case amountCompleted := <-r.completions:
+ usedCapacity -= amountCompleted
+ if usedCapacity < 0 {
+ panic(fmt.Sprintf("usedCapacity < 0: %v", usedCapacity))
}
- case amount := <-r.released:
- curMemory -= int64(amount)
case <-r.stop:
return
}
+
+ if currentRequest != nil {
+ accepted := false
+ if usedCapacity == 0 {
+ accepted = true
+ } else {
+ if capacity >= usedCapacity+currentRequest.size {
+ accepted = true
+ }
+ }
+ if accepted {
+ usedCapacity += currentRequest.size
+ currentRequest.serviced <- struct{}{}
+ currentRequest = nil
+ }
+ }
}
}
+
+// A CPURateLimiter limits the number of active calls based on CPU requirements
+type CPURateLimiter struct {
+ impl *RateLimit
+}
+
+func NewCPURateLimiter(capacity int64) *CPURateLimiter {
+ if capacity <= 0 {
+ capacity = int64(runtime.NumCPU())
+ }
+ impl := NewRateLimit(capacity)
+ return &CPURateLimiter{impl: impl}
+}
+
+func (e CPURateLimiter) Request() {
+ e.impl.Request(1)
+}
+
+func (e CPURateLimiter) Finish() {
+ e.impl.Finish(1)
+}
+
+func (e CPURateLimiter) Stop() {
+ e.impl.Stop()
+}
+
+// A MemoryRateLimiter limits the number of active calls based on Memory requirements
+type MemoryRateLimiter struct {
+ *RateLimit
+}
+
+func NewMemoryRateLimiter(capacity int64) *MemoryRateLimiter {
+ if capacity <= 0 {
+ capacity = 512 * 1024 * 1024 // 512MB
+ }
+ impl := NewRateLimit(capacity)
+ return &MemoryRateLimiter{RateLimit: impl}
+}