From 071488bfaada18897cb19ff3e568d837e0260bc4 Mon Sep 17 00:00:00 2001
From: Matthew Sackman <matthew@rabbitmq.com>
Date: Wed, 12 Oct 2011 14:40:12 +0100
Subject: cosmetic, and be somewhat smarter about deciding the minimum length
 of q3 (now must end on a segment boundary - minor optimisation)

---
 src/lqueue.erl                | 10 +++++-----
 src/rabbit_variable_queue.erl | 13 ++++++++++---
 2 files changed, 15 insertions(+), 8 deletions(-)

diff --git a/src/lqueue.erl b/src/lqueue.erl
index 80fb1fd9..9f58b250 100644
--- a/src/lqueue.erl
+++ b/src/lqueue.erl
@@ -119,10 +119,10 @@ foldr(Fun, Init, Q) ->
 len({L, _Q, _I, _O}) ->
     L.
 
-peek({0, _, _, _}) -> empty;
-peek({1, _, V, empty}) -> V;
-peek({_L, _Q, _I, O}) -> O.
+peek({0, _, _, _})       -> empty;
+peek({1, _, V, empty})   -> V;
+peek({_L, _Q, _I, O})    -> O.
 
-peek_r({0, _, _, _}) -> empty;
+peek_r({0, _, _, _})     -> empty;
 peek_r({1, _, empty, V}) -> V;
-peek_r({_L, _Q, I, _O}) -> I.
+peek_r({_L, _Q, I, _O})  -> I.
diff --git a/src/rabbit_variable_queue.erl b/src/rabbit_variable_queue.erl
index 2df83046..44d7d73c 100644
--- a/src/rabbit_variable_queue.erl
+++ b/src/rabbit_variable_queue.erl
@@ -1482,11 +1482,18 @@ permitted_beta_count(#vqstate { len = 0 }) ->
     infinity;
 permitted_beta_count(#vqstate { target_ram_count = 0 }) ->
     rabbit_queue_index:next_segment_boundary(0);
-permitted_beta_count(#vqstate { target_ram_count = TargetRamCount,
+permitted_beta_count(#vqstate { q3 = Q3,
+                                target_ram_count = TargetRamCount,
                                 len = Len }) ->
     BetaDelta = lists:max([0, Len - TargetRamCount]),
-    lists:max([BetaDelta - ((BetaDelta * BetaDelta) div Len),
-               rabbit_queue_index:next_segment_boundary(0)]).
+    Q3SizeLimit =
+        case ?QUEUE:peek(Q3) of
+            empty ->
+                0;
+            {value, #msg_status { seq_id = SeqId }} ->
+                rabbit_queue_index:next_segment_boundary(SeqId) - SeqId
+        end,
+    lists:max([BetaDelta - ((BetaDelta * BetaDelta) div Len), Q3SizeLimit]).
 
 chunk_size(Current, Permitted)
   when Permitted =:= infinity orelse Permitted >= Current ->
-- 
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