epoll: use ilist:generic_list instead of ilist:ilist

ilist:generic_list works faster than ilist:ilist.

Here is a beanchmark test to measure performance of epoll_wait, when readyList
isn't empty. It shows about 30% better performance with these changes.

Benchmark           Time(ns)        CPU(ns)     Iterations
Before:
BM_EpollAllEvents      46725          46899          14286

After:
BM_EpollAllEvents      33167          33300          18919
PiperOrigin-RevId: 240185278
Change-Id: I3e33f9b214db13ab840b91613400525de5b58d18

3 files changed, 28 insertions, 18 deletions

diff --git a/pkg/sentry/kernel/epoll/BUILD b/pkg/sentry/kernel/epoll/BUILD
index 1567d5050..3ac59e13e 100644
--- a/pkg/sentry/kernel/epoll/BUILD
+++ b/pkg/sentry/kernel/epoll/BUILD
@@ -1,17 +1,30 @@
 package(licenses = ["notice"])
 
+load("//tools/go_generics:defs.bzl", "go_template_instance")
 load("//tools/go_stateify:defs.bzl", "go_library", "go_test")
 
+go_template_instance(
+    name = "epoll_list",
+    out = "epoll_list.go",
+    package = "epoll",
+    prefix = "pollEntry",
+    template = "//pkg/ilist:generic_list",
+    types = {
+        "Element": "*pollEntry",
+        "Linker": "*pollEntry",
+    },
+)
+
 go_library(
     name = "epoll",
     srcs = [
         "epoll.go",
+        "epoll_list.go",
         "epoll_state.go",
     ],
     importpath = "gvisor.googlesource.com/gvisor/pkg/sentry/kernel/epoll",
     visibility = ["//pkg/sentry:internal"],
     deps = [
-        "//pkg/ilist",
         "//pkg/refs",
         "//pkg/sentry/context",
         "//pkg/sentry/fs",
diff --git a/pkg/sentry/kernel/epoll/epoll.go b/pkg/sentry/kernel/epoll/epoll.go
index 502395f18..61c0fb7c5 100644
--- a/pkg/sentry/kernel/epoll/epoll.go
+++ b/pkg/sentry/kernel/epoll/epoll.go
@@ -21,7 +21,6 @@ import (
 	"sync"
 	"syscall"
 
-	"gvisor.googlesource.com/gvisor/pkg/ilist"
 	"gvisor.googlesource.com/gvisor/pkg/refs"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/context"
 	"gvisor.googlesource.com/gvisor/pkg/sentry/fs"
@@ -70,7 +69,7 @@ type FileIdentifier struct {
 //
 // +stateify savable
 type pollEntry struct {
-	ilist.Entry
+	pollEntryEntry
 	file     *refs.WeakRef  `state:"manual"`
 	id       FileIdentifier `state:"wait"`
 	userData [2]int32
@@ -84,7 +83,7 @@ type pollEntry struct {
 	// struct, while state framework currently does not support such
 	// in-struct pointers. Instead, EventPoll will properly set this field
 	// in its loading logic.
-	curList *ilist.List `state:"nosave"`
+	curList *pollEntryList `state:"nosave"`
 }
 
 // WeakRefGone implements refs.WeakRefUser.WeakRefGone.
@@ -133,9 +132,9 @@ type EventPoll struct {
 	//	disabledList -- when the entry is disabled. This happens when
 	//		a one-shot entry gets delivered via readEvents().
 	listsMu      sync.Mutex `state:"nosave"`
-	readyList    ilist.List
-	waitingList  ilist.List
-	disabledList ilist.List
+	readyList    pollEntryList
+	waitingList  pollEntryList
+	disabledList pollEntryList
 }
 
 // cycleMu is used to serialize all the cycle checks. This is only used when
@@ -189,7 +188,7 @@ func (e *EventPoll) eventsAvailable() bool {
 	e.listsMu.Lock()
 
 	for it := e.readyList.Front(); it != nil; {
-		entry := it.(*pollEntry)
+		entry := it
 		it = it.Next()
 
 		// If the entry is ready, we know 'e' has at least one entry
@@ -225,14 +224,14 @@ func (e *EventPoll) Readiness(mask waiter.EventMask) waiter.EventMask {
 
 // ReadEvents returns up to max available events.
 func (e *EventPoll) ReadEvents(max int) []Event {
-	var local ilist.List
+	var local pollEntryList
 	var ret []Event
 
 	e.listsMu.Lock()
 
 	// Go through all entries we believe may be ready.
 	for it := e.readyList.Front(); it != nil && len(ret) < max; {
-		entry := it.(*pollEntry)
+		entry := it
 		it = it.Next()
 
 		// Check the entry's readiness. It it's not really ready, we
diff --git a/pkg/sentry/kernel/epoll/epoll_state.go b/pkg/sentry/kernel/epoll/epoll_state.go
index 7f3e2004a..f6e3e4825 100644
--- a/pkg/sentry/kernel/epoll/epoll_state.go
+++ b/pkg/sentry/kernel/epoll/epoll_state.go
@@ -15,7 +15,6 @@
 package epoll
 
 import (
-	"gvisor.googlesource.com/gvisor/pkg/ilist"
 	"gvisor.googlesource.com/gvisor/pkg/refs"
 	"gvisor.googlesource.com/gvisor/pkg/waiter"
 )
@@ -33,18 +32,17 @@ func (e *EventPoll) afterLoad() {
 	e.listsMu.Lock()
 	defer e.listsMu.Unlock()
 
-	for _, ls := range []*ilist.List{&e.waitingList, &e.readyList, &e.disabledList} {
+	for _, ls := range []*pollEntryList{&e.waitingList, &e.readyList, &e.disabledList} {
 		for it := ls.Front(); it != nil; it = it.Next() {
-			it.(*pollEntry).curList = ls
+			it.curList = ls
 		}
 	}
 
 	for it := e.waitingList.Front(); it != nil; it = it.Next() {
-		p := it.(*pollEntry)
-		if p.id.File.Readiness(p.mask) != 0 {
-			e.waitingList.Remove(p)
-			e.readyList.PushBack(p)
-			p.curList = &e.readyList
+		if it.id.File.Readiness(it.mask) != 0 {
+			e.waitingList.Remove(it)
+			e.readyList.PushBack(it)
+			it.curList = &e.readyList
 			e.Notify(waiter.EventIn)
 		}
 	}