From fd4c8c38051f9dad028e4e43e0eb39ba412b2c0a Mon Sep 17 00:00:00 2001
From: Matthew Bouyack <mbouyack@google.com>
Date: Fri, 7 Oct 2016 14:26:47 -0700
Subject: [PATCH] Use snprintf for SurfaceFlinger fence name

snprintf is significantly faster than String8::format
This change saves ~50us per frame on Android Wear

Change-Id: I6ac47c2434662ca561208daae232f02a9f136aaf
---
 include/ui/Fence.h        |  3 +++
 libs/gui/ConsumerBase.cpp |  5 +++--
 libs/ui/Fence.cpp         | 15 ++++++++++-----
 3 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/include/ui/Fence.h b/include/ui/Fence.h
index b431bd52aa..23a8658f51 100644
--- a/include/ui/Fence.h
+++ b/include/ui/Fence.h
@@ -79,6 +79,9 @@ public:
     // becomes signaled when both f1 and f2 are signaled (even if f1 or f2 is
     // destroyed before it becomes signaled).  The name argument specifies the
     // human-readable name to associated with the new Fence object.
+    static sp<Fence> merge(const char* name, const sp<Fence>& f1,
+            const sp<Fence>& f2);
+
     static sp<Fence> merge(const String8& name, const sp<Fence>& f1,
             const sp<Fence>& f2);
 
diff --git a/libs/gui/ConsumerBase.cpp b/libs/gui/ConsumerBase.cpp
index a1bdf4a4a1..e7bc7dc73d 100644
--- a/libs/gui/ConsumerBase.cpp
+++ b/libs/gui/ConsumerBase.cpp
@@ -315,9 +315,10 @@ status_t ConsumerBase::addReleaseFenceLocked(int slot,
     if (!mSlots[slot].mFence.get()) {
         mSlots[slot].mFence = fence;
     } else {
+        char fenceName[32] = {};
+        snprintf(fenceName, 32, "%.28s:%d", mName.string(), slot);
         sp<Fence> mergedFence = Fence::merge(
-                String8::format("%.28s:%d", mName.string(), slot),
-                mSlots[slot].mFence, fence);
+                fenceName, mSlots[slot].mFence, fence);
         if (!mergedFence.get()) {
             CB_LOGE("failed to merge release fences");
             // synchronization is broken, the best we can do is hope fences
diff --git a/libs/ui/Fence.cpp b/libs/ui/Fence.cpp
index bf24ffb7e0..7cf8233820 100644
--- a/libs/ui/Fence.cpp
+++ b/libs/ui/Fence.cpp
@@ -72,7 +72,7 @@ status_t Fence::waitForever(const char* logname) {
     return err < 0 ? -errno : status_t(NO_ERROR);
 }
 
-sp<Fence> Fence::merge(const String8& name, const sp<Fence>& f1,
+sp<Fence> Fence::merge(const char* name, const sp<Fence>& f1,
         const sp<Fence>& f2) {
     ATRACE_CALL();
     int result;
@@ -80,24 +80,29 @@ sp<Fence> Fence::merge(const String8& name, const sp<Fence>& f1,
     // valid fence (e.g. NO_FENCE) we merge the one valid fence with itself so
     // that a new fence with the given name is created.
     if (f1->isValid() && f2->isValid()) {
-        result = sync_merge(name.string(), f1->mFenceFd, f2->mFenceFd);
+        result = sync_merge(name, f1->mFenceFd, f2->mFenceFd);
     } else if (f1->isValid()) {
-        result = sync_merge(name.string(), f1->mFenceFd, f1->mFenceFd);
+        result = sync_merge(name, f1->mFenceFd, f1->mFenceFd);
     } else if (f2->isValid()) {
-        result = sync_merge(name.string(), f2->mFenceFd, f2->mFenceFd);
+        result = sync_merge(name, f2->mFenceFd, f2->mFenceFd);
     } else {
         return NO_FENCE;
     }
     if (result == -1) {
         status_t err = -errno;
         ALOGE("merge: sync_merge(\"%s\", %d, %d) returned an error: %s (%d)",
-                name.string(), f1->mFenceFd, f2->mFenceFd,
+                name, f1->mFenceFd, f2->mFenceFd,
                 strerror(-err), err);
         return NO_FENCE;
     }
     return sp<Fence>(new Fence(result));
 }
 
+sp<Fence> Fence::merge(const String8& name, const sp<Fence>& f1,
+        const sp<Fence>& f2) {
+    return merge(name.string(), f1, f2);
+}
+
 int Fence::dup() const {
     return ::dup(mFenceFd);
 }
-- 
2.11.0