blob: dfc7f5aae852f9c4fd9a071aa4d7b964d32c2e0e (
plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
|
From 7abd305607938b846da1a37dd1bda7bf7d47dba5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Edwin=20T=C3=B6r=C3=B6k?= <edwin.torok@cloud.com>
Date: Wed, 31 Jan 2024 10:52:55 +0000
Subject: [PATCH 58/67] tools/oxenstored: Use Map instead of Hashtbl for quotas
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit
On a stress test running 1000 VMs flamegraphs have shown that
`oxenstored` spends a large amount of time in `Hashtbl.copy` and the GC.
Hashtable complexity:
* read/write: O(1) average
* copy: O(domains) -- copying the entire table
Map complexity:
* read/write: O(log n) worst case
* copy: O(1) -- a word copy
We always perform at least one 'copy' when processing each xenstore
packet (regardless whether it is a readonly operation or inside a
transaction or not), so the actual complexity per packet is:
* Hashtbl: O(domains)
* Map: O(log domains)
Maps are the clear winner, and a better fit for the immutable xenstore
tree.
Signed-off-by: Edwin Török <edwin.torok@cloud.com>
Acked-by: Christian Lindig <christian.lindig@cloud.com>
(cherry picked from commit b6cf604207fd0a04451a48f2ce6d05fb66c612ab)
---
tools/ocaml/xenstored/quota.ml | 65 ++++++++++++++++++----------------
1 file changed, 34 insertions(+), 31 deletions(-)
diff --git a/tools/ocaml/xenstored/quota.ml b/tools/ocaml/xenstored/quota.ml
index 6e3d6401ae..ee8dd22581 100644
--- a/tools/ocaml/xenstored/quota.ml
+++ b/tools/ocaml/xenstored/quota.ml
@@ -23,66 +23,69 @@ let activate = ref true
let maxent = ref (1000)
let maxsize = ref (2048)
+module Domid = struct
+ type t = Xenctrl.domid
+ let compare (a:t) (b:t) = compare a b
+end
+
+module DomidMap = Map.Make(Domid)
+
type t = {
maxent: int; (* max entities per domU *)
maxsize: int; (* max size of data store in one node *)
- cur: (Xenctrl.domid, int) Hashtbl.t; (* current domains quota *)
+ mutable cur: int DomidMap.t; (* current domains quota *)
}
let to_string quota domid =
- if Hashtbl.mem quota.cur domid
- then Printf.sprintf "dom%i quota: %i/%i" domid (Hashtbl.find quota.cur domid) quota.maxent
- else Printf.sprintf "dom%i quota: not set" domid
+ try
+ Printf.sprintf "dom%i quota: %i/%i" domid (DomidMap.find domid quota.cur) quota.maxent
+ with Not_found ->
+ Printf.sprintf "dom%i quota: not set" domid
let create () =
- { maxent = !maxent; maxsize = !maxsize; cur = Hashtbl.create 100; }
+ { maxent = !maxent; maxsize = !maxsize; cur = DomidMap.empty; }
-let copy quota = { quota with cur = (Hashtbl.copy quota.cur) }
+let copy quota = { quota with cur = quota.cur }
-let del quota id = Hashtbl.remove quota.cur id
+let del quota id = { quota with cur = DomidMap.remove id quota.cur }
let _check quota id size =
if size > quota.maxsize then (
warn "domain %u err create entry: data too big %d" id size;
raise Data_too_big
);
- if id > 0 && Hashtbl.mem quota.cur id then
- let entry = Hashtbl.find quota.cur id in
+ if id > 0 then
+ try
+ let entry = DomidMap.find id quota.cur in
if entry >= quota.maxent then (
warn "domain %u cannot create entry: quota reached" id;
raise Limit_reached
)
+ with Not_found -> ()
let check quota id size =
if !activate then
_check quota id size
-let get_entry quota id = Hashtbl.find quota.cur id
+let find_or_zero quota_cur id =
+ try DomidMap.find id quota_cur with Not_found -> 0
-let set_entry quota id nb =
- if nb = 0
- then Hashtbl.remove quota.cur id
- else begin
- if Hashtbl.mem quota.cur id then
- Hashtbl.replace quota.cur id nb
- else
- Hashtbl.add quota.cur id nb
- end
+let update_entry quota_cur id diff =
+ let nb = diff + find_or_zero quota_cur id in
+ if nb = 0 then DomidMap.remove id quota_cur
+ else DomidMap.add id nb quota_cur
let del_entry quota id =
- try
- let nb = get_entry quota id in
- set_entry quota id (nb - 1)
- with Not_found -> ()
+ quota.cur <- update_entry quota.cur id (-1)
let add_entry quota id =
- let nb = try get_entry quota id with Not_found -> 0 in
- set_entry quota id (nb + 1)
-
-let add quota diff =
- Hashtbl.iter (fun id nb -> set_entry quota id (get_entry quota id + nb)) diff.cur
+ quota.cur <- update_entry quota.cur id (+1)
let merge orig_quota mod_quota dest_quota =
- Hashtbl.iter (fun id nb -> let diff = nb - (try get_entry orig_quota id with Not_found -> 0) in
- if diff <> 0 then
- set_entry dest_quota id ((try get_entry dest_quota id with Not_found -> 0) + diff)) mod_quota.cur
+ let fold_merge id nb dest =
+ match nb - find_or_zero orig_quota.cur id with
+ | 0 -> dest (* not modified *)
+ | diff -> update_entry dest id diff (* update with [x=x+diff] *)
+ in
+ dest_quota.cur <- DomidMap.fold fold_merge mod_quota.cur dest_quota.cur
+ (* dest_quota = dest_quota + (mod_quota - orig_quota) *)
--
2.44.0
|
GitWeb