File 2861-Convert-inet_cache-to-a-set.patch of Package erlang

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File 2861-Convert-inet_cache-to-a-set.patch of Package erlang (Revision 54412ea392063e09a486a38b36b3d904)

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From 76a2300189193c73e2e09f6aa39218ea5eac762c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jos=C3=A9=20Valim?= <jose.valim@dashbit.co>
Date: Sat, 28 Nov 2020 12:44:51 +0100
Subject: [PATCH] Convert inet_cache to a set

This patch is just a refactoring but it should provide
faster operations at the cost of slightly higher storage
(which is acceptable since the table is relatively small).
This will also make it possible to have decentralized
lookups in the future.
---
 lib/kernel/src/inet_db.erl | 104 +++++++++++++++++--------------------
 1 file changed, 49 insertions(+), 55 deletions(-)

diff --git a/lib/kernel/src/inet_db.erl b/lib/kernel/src/inet_db.erl
index 7fcbc67d9c..1dae042d1f 100644
--- a/lib/kernel/src/inet_db.erl
+++ b/lib/kernel/src/inet_db.erl
@@ -752,9 +752,7 @@ res_lookup_type(Domain,Type,RRs) ->
 gethostbyaddr(IP) ->
     case dnip(IP) of
 	{ok, {IP1, HType, HLen, DnIP}} ->
-	    RRs = match_rr(#dns_rr { domain = DnIP, class = in, type = ptr,
-				     cnt = '_', tm = '_', ttl = '_',
-				     bm = '_', func = '_', data = '_' }),
+	    RRs = match_rr({DnIP, in, ptr}),
 	    ent_gethostbyaddr(RRs,  IP1, HType, HLen);
 	Error -> Error
     end.
@@ -899,8 +897,7 @@ init([]) ->
     end,
     Db = ets:new(inet_db, [public, named_table]),
     reset_db(Db),
-    CacheOpts = [public, bag, {keypos,#dns_rr.domain}, named_table],
-    Cache = ets:new(inet_cache, CacheOpts),
+    Cache = ets:new(inet_cache, [public, set, named_table]),
     HostsByname = ets:new(inet_hosts_byname, [named_table]),
     HostsByaddr = ets:new(inet_hosts_byaddr, [named_table]),
     HostsFileByname = ets:new(inet_hosts_file_byname, [named_table]),
@@ -992,11 +989,11 @@ handle_call(Request, From, #state{db=Db}=State) ->
 	{del_rr, RR} when is_record(RR, dns_rr) ->
 	    %% note. del_rr will handle wildcards !!!
 	    Cache = State#state.cache,
-	    ets:match_delete(Cache, RR),
+	    ets:delete(Cache, cache_key(RR)),
 	    {reply, ok, State};
 
 	{lookup_rr, Domain, Class, Type} ->
-	    {reply, do_lookup_rr(Domain, Class, Type), State};
+	    {reply, match_rr({Domain, Class, Type}), State};
 
 	{listop, Opt, Op, E} ->
 	    El = [E],
@@ -1166,7 +1163,7 @@ handle_call(Request, From, #state{db=Db}=State) ->
 	    {reply, ok, State};
 
 	clear_cache ->
-	    ets:match_delete(State#state.cache, '_'),
+	    ets:delete_all_objects(State#state.cache),
 	    {reply, ok, State};
 
 	reset ->
@@ -1621,46 +1618,41 @@ do_add_rr(RR, Db, State) ->
     TM = times(),
     case alloc_entry(Db, CacheDb, TM) of
 	true ->
-	    cache_rr(Db, CacheDb, RR#dns_rr{tm = TM, cnt = TM});
+	    cache_rr(CacheDb, RR#dns_rr{tm = TM, cnt = TM});
 	_ ->
 	    false
     end.
 
-cache_rr(_Db, Cache, RR) ->
-    %% delete possible old entry
-    ets:match_delete(Cache, RR#dns_rr{cnt = '_', tm = '_', ttl = '_',
-				      bm = '_', func = '_'}),
-    ets:insert(Cache, RR).
+cache_rr(Cache, RR) ->
+    ets:insert(Cache, {cache_key(RR), RR}).
 
 times() ->
     erlang:monotonic_time(second).
     %% erlang:convert_time_unit(erlang:monotonic_time() - erlang:system_info(start_time),
     %%     		     native, second).
 
-%% lookup and remove old entries
-
-do_lookup_rr(Domain, Class, Type) ->
-    match_rr(#dns_rr{domain = tolower(Domain), class = Class,type = Type,
-		     cnt = '_', tm = '_', ttl = '_',
-		     bm = '_', func = '_', data = '_'}).
-
-match_rr(RR) ->
-    filter_rr(ets:match_object(inet_cache, RR), times()).
-
-
-%% filter old resource records and update access count
+%% match and remove old entries
+
+match_rr({_, _, _} = Key) ->
+    Time = times(),
+    case ets:lookup(inet_cache, Key) of
+	[{_,RR}] when RR#dns_rr.ttl =:= 0 -> %% at least once
+	    ets:delete(inet_cache, Key),
+	    [RR];
+	[{_,RR}] when RR#dns_rr.tm + RR#dns_rr.ttl < Time ->
+	    ets:delete(inet_cache, Key),
+	    [];
+	[{_,RR}] ->
+        %% This may fail if cache pruning removes this entry
+        %% at the same time we are updating it, so ignore the result.
+	    _ = ets:update_element(inet_cache, Key, {2, RR#dns_rr{cnt = Time}}),
+	    [RR];
+	[] ->
+	    []
+    end.
 
-filter_rr([RR | RRs], Time) when RR#dns_rr.ttl =:= 0 -> %% at least once
-    ets:match_delete(inet_cache, RR),
-    [RR | filter_rr(RRs, Time)];
-filter_rr([RR | RRs], Time) when RR#dns_rr.tm + RR#dns_rr.ttl < Time ->
-    ets:match_delete(inet_cache, RR),
-    filter_rr(RRs, Time);
-filter_rr([RR | RRs], Time) ->
-    ets:match_delete(inet_cache, RR),
-    ets:insert(inet_cache, RR#dns_rr { cnt = Time }),
-    [RR | filter_rr(RRs, Time)];
-filter_rr([], _Time) ->  [].
+cache_key(#dns_rr{domain = Domain, class = Class, type = Type}) ->
+    {Domain, Class, Type}.
 
 %% Lower case the domain name before storage.
 %%
@@ -1746,16 +1738,17 @@ do_refresh_cache(CacheDb) ->
 do_refresh_cache('$end_of_table', _, _, OldestT) ->
     OldestT;
 do_refresh_cache(Key, CacheDb, Now, OldestT) ->
-    Fun = fun(RR, T) when RR#dns_rr.tm + RR#dns_rr.ttl < Now ->
-		  ets:match_delete(CacheDb, RR),
-		  T;
-	     (#dns_rr{cnt = C}, T) when C < T ->
-		  C;
-	     (_, T) ->
-		  T
-	  end,
     Next = ets:next(CacheDb, Key),
-    OldT = lists:foldl(Fun, OldestT, ets:lookup(CacheDb, Key)),
+    OldT =
+        case ets:lookup(CacheDb, Key) of
+	    [{_,RR}] when RR#dns_rr.tm + RR#dns_rr.ttl < Now ->
+		ets:delete(CacheDb, Key),
+		OldestT;
+	     [{_,#dns_rr{cnt = C}}] when C < OldestT ->
+		C;
+	     _ ->
+		OldestT
+	end,
     do_refresh_cache(Next, CacheDb, Now, OldT).
 
 %% -------------------------------------------------------------------
@@ -1800,17 +1793,18 @@ delete_older(CacheDb, TM, N) ->
 
 delete_older('$end_of_table', _, _, _, M) ->
     M;
-delete_older(_, _, _, N, M) when N =< M ->
+delete_older(_, _, _, M, M) ->
     M;
-delete_older(Domain, CacheDb, TM, N, M) ->
-    Next = ets:next(CacheDb, Domain),
-    Fun = fun(RR, MM) when RR#dns_rr.cnt =< TM ->
-		  ets:match_delete(CacheDb, RR),
-		  MM + 1;
-	     (_, MM) ->
-		  MM
+delete_older(Key, CacheDb, TM, N, M) ->
+    Next = ets:next(CacheDb, Key),
+    M1 =
+	case ets:lookup(CacheDb, Key) of
+	    [{_,RR}] when RR#dns_rr.cnt =< TM ->
+		ets:delete(CacheDb, Key),
+		M + 1;
+	    _ ->
+		M
 	  end,
-    M1 = lists:foldl(Fun, M, ets:lookup(CacheDb, Domain)),
     delete_older(Next, CacheDb, TM, N, M1).
 
 
-- 
2.26.2

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File 2861-Convert-inet_cache-to-a-set.patch of Package erlang (Revision 54412ea392063e09a486a38b36b3d904)

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