reimplemnt oobgc algorithm

lib/middleware/unicorn_oobgc.rb

@@ -5,8 +5,18 @@
 #  hook unicorn
 module Middleware::UnicornOobgc
 
-  MIN_REQUESTS_PER_OOBGC = 5
+  MIN_REQUESTS_PER_OOBGC = 3
-  MAX_DELTAS = 25
+
+  def verbose(msg=nil)
+    @verbose ||= ENV["OOBGC_VERBOSE"] == "1" ? :true : :false
+    if @verbose == :true
+      if(msg)
+        puts msg
+      end
+
+      true
+    end
+  end
 
   def self.init
     # hook up HttpServer intercept
@@ -17,21 +27,22 @@ module Middleware::UnicornOobgc
     puts "Attempted to patch Unicorn but it is not loaded"
   end
 
+  # the closer this is to the GC run the more accurate it is
+  def estimate_live_num_at_gc(stat)
+    stat[:heap_live_num] + stat[:heap_free_num]
+  end
+
   def process_client(client)
     stat = GC.stat
 
-    @previous_deltas ||= []
     @num_requests ||= 0
     @num_requests += 1
 
-    # only track N deltas
-    if @previous_deltas.length > MAX_DELTAS
-      @previous_deltas.delete_at(0)
-    end
-
     gc_count = stat[:count]
     live_num = stat[:heap_live_num]
 
+    @expect_gc_at ||= estimate_live_num_at_gc(stat)
+
     super(client) # Unicorn::HttpServer#process_client
 
     # at this point client is serviced
@@ -41,25 +52,32 @@ module Middleware::UnicornOobgc
 
     # no GC happened during the request
     if new_gc_count == gc_count
-      @previous_deltas << (new_live_num - live_num)
+      delta = new_live_num - live_num
 
-      if @gc_live_num && @num_requests > MIN_REQUESTS_PER_OOBGC
+      @max_delta ||= delta
-        largest = @previous_deltas.max
-        if (largest * 3) + new_live_num > @gc_live_num
-          # While tuning consider printing this out, each time this happens you saved
-          # a user from running a GC inline
 
-          # t = Time.now
+      if delta > @max_delta
-          GC.start
+        new_delta = (delta * 1.5).to_i
-          # puts "OobGC invoked req count: #{@num_requests} largest delta: #{largest} #{((Time.now - t) * 1000).to_i}ms saved"
+        @max_delta = [new_delta, delta].min
-          @num_requests = 0
+      else
+        new_delta = (delta * 0.99).to_i
+        @max_delta = [new_delta, delta].max
       end
+
+      if @num_requests > MIN_REQUESTS_PER_OOBGC && @max_delta * 2 + new_live_num > @expect_gc_at
+        t = Time.now
+        GC.start
+        stat = GC.stat
+        @expect_gc_at = estimate_live_num_at_gc(stat)
+        verbose "OobGC hit pid: #{Process.pid} req: #{@num_requests} max delta: #{@max_delta} expect at: #{@expect_gc_at} #{((Time.now - t) * 1000).to_i}ms saved"
+        @num_requests = 0
       end
     else
-      puts "OobGC: GC live num adjusted: old live_num #{@gc_live_num}  new: #{live_num} - reqs since GC: #{@num_requests} largest delta: #{@previous_deltas.max}"
+
+      verbose "OobGC miss pid: #{Process.pid} reqs: #{@num_requests}"
 
       @num_requests = 0
-      @gc_live_num = live_num
+      @expect_gc_at = estimate_live_num_at_gc(stat)
 
     end