labels: Halve CIDR labels LRU cache size

[ upstream commit 6f1253e ]

After fixing the GetCIDRLabels implementation to generate all the labels
required for a CIDR, the heap usage of the LRU cache increased 10x in
the worst case (all IPv6 labels).  To reduce heap usage, the cache size
is halved, resulting in ~25 MiB in the IPv6 only case with roughly the
same performance.

=== RUN   TestCIDRLabelsCacheHeapUsageIPv4
    cidr_test.go:527: Memoization map heap usage: 1714.41 KiB
--- PASS: TestCIDRLabelsCacheHeapUsageIPv4 (0.67s)
=== RUN   TestCIDRLabelsCacheHeapUsageIPv6
    cidr_test.go:571: Memoization map heap usage: 26527.13 KiB
--- PASS: TestCIDRLabelsCacheHeapUsageIPv6 (0.71s)

name                             old time/op    new time/op    delta
GetCIDRLabels/0.0.0.0/0-8           198ns ±40%     238ns ±34%    ~     (p=0.325 n=10+10)
GetCIDRLabels/10.16.0.0/16-8       1.32µs ± 8%    1.33µs ± 8%    ~     (p=0.812 n=10+10)
GetCIDRLabels/192.0.2.3/32-8       2.41µs ± 3%    2.39µs ± 5%    ~     (p=0.278 n=10+9)
GetCIDRLabels/192.0.2.3/24-8       2.05µs ± 2%    2.05µs ± 1%    ~     (p=0.948 n=9+9)
GetCIDRLabels/192.0.2.0/24-8       2.05µs ± 2%    2.04µs ± 1%    ~     (p=0.797 n=9+8)
GetCIDRLabels/::/0-8                277ns ±31%     257ns ± 1%    ~     (p=0.349 n=10+8)
GetCIDRLabels/fdff::ff/128-8       9.02µs ± 6%    8.80µs ± 3%    ~     (p=0.077 n=9+9)
GetCIDRLabels/f00d:42::ff/128-8    9.40µs ± 6%    9.01µs ± 5%  -4.12%  (p=0.035 n=10+10)
GetCIDRLabels/f00d:42::ff/96-8     7.78µs ± 4%    7.58µs ± 1%  -2.59%  (p=0.011 n=8+9)
GetCIDRLabelsConcurrent/1-8         189µs ± 8%     173µs ± 3%  -8.85%  (p=0.000 n=10+9)
GetCIDRLabelsConcurrent/2-8         350µs ± 2%     346µs ± 1%  -1.05%  (p=0.001 n=8+8)
GetCIDRLabelsConcurrent/4-8         703µs ± 1%     692µs ± 1%  -1.59%  (p=0.000 n=9+9)
GetCIDRLabelsConcurrent/16-8       2.97ms ± 7%    2.91ms ± 1%    ~     (p=0.122 n=10+8)
GetCIDRLabelsConcurrent/32-8       5.81ms ± 1%    5.77ms ± 1%  -0.57%  (p=0.011 n=8+9)
GetCIDRLabelsConcurrent/48-8       8.87ms ± 6%    8.71ms ± 1%    ~     (p=0.139 n=9+8)

name                             old alloc/op   new alloc/op   delta
GetCIDRLabels/0.0.0.0/0-8            624B ± 0%      624B ± 0%    ~     (all equal)
GetCIDRLabels/10.16.0.0/16-8       2.40kB ± 0%    2.40kB ± 0%    ~     (all equal)
GetCIDRLabels/192.0.2.3/32-8       5.01kB ± 0%    5.01kB ± 0%    ~     (all equal)
GetCIDRLabels/192.0.2.3/24-8       4.93kB ± 0%    4.93kB ± 0%    ~     (all equal)
GetCIDRLabels/192.0.2.0/24-8       4.93kB ± 0%    4.93kB ± 0%    ~     (all equal)
GetCIDRLabels/::/0-8                 624B ± 0%      624B ± 0%    ~     (all equal)
GetCIDRLabels/fdff::ff/128-8       18.5kB ± 0%    18.5kB ± 0%    ~     (all equal)
GetCIDRLabels/f00d:42::ff/128-8    18.5kB ± 0%    18.5kB ± 0%    ~     (all equal)
GetCIDRLabels/f00d:42::ff/96-8     18.5kB ± 0%    18.5kB ± 0%    ~     (all equal)
GetCIDRLabelsConcurrent/1-8         321kB ± 0%     321kB ± 0%    ~     (p=0.645 n=10+10)
GetCIDRLabelsConcurrent/2-8         641kB ± 0%     641kB ± 0%    ~     (p=0.796 n=10+10)
GetCIDRLabelsConcurrent/4-8        1.28MB ± 0%    1.28MB ± 0%    ~     (p=0.353 n=10+10)
GetCIDRLabelsConcurrent/16-8       5.13MB ± 0%    5.13MB ± 0%    ~     (p=0.083 n=10+8)
GetCIDRLabelsConcurrent/32-8       10.3MB ± 0%    10.3MB ± 0%    ~     (p=0.481 n=10+10)
GetCIDRLabelsConcurrent/48-8       15.4MB ± 0%    15.4MB ± 0%    ~     (p=0.796 n=10+10)

name                             old allocs/op  new allocs/op  delta
GetCIDRLabels/0.0.0.0/0-8            2.00 ± 0%      2.00 ± 0%    ~     (all equal)
GetCIDRLabels/10.16.0.0/16-8         2.00 ± 0%      2.00 ± 0%    ~     (all equal)
GetCIDRLabels/192.0.2.3/32-8         2.00 ± 0%      2.00 ± 0%    ~     (all equal)
GetCIDRLabels/192.0.2.3/24-8         2.00 ± 0%      2.00 ± 0%    ~     (all equal)
GetCIDRLabels/192.0.2.0/24-8         2.00 ± 0%      2.00 ± 0%    ~     (all equal)
GetCIDRLabels/::/0-8                 2.00 ± 0%      2.00 ± 0%    ~     (all equal)
GetCIDRLabels/fdff::ff/128-8         3.00 ± 0%      3.00 ± 0%    ~     (all equal)
GetCIDRLabels/f00d:42::ff/128-8      3.00 ± 0%      3.00 ± 0%    ~     (all equal)
GetCIDRLabels/f00d:42::ff/96-8       3.00 ± 0%      3.00 ± 0%    ~     (all equal)
GetCIDRLabelsConcurrent/1-8           138 ± 0%       138 ± 0%    ~     (all equal)
GetCIDRLabelsConcurrent/2-8           277 ± 0%       277 ± 0%    ~     (all equal)
GetCIDRLabelsConcurrent/4-8           555 ± 0%       555 ± 0%    ~     (all equal)
GetCIDRLabelsConcurrent/16-8        2.22k ± 0%     2.22k ± 0%    ~     (p=0.176 n=10+7)
GetCIDRLabelsConcurrent/32-8        4.44k ± 0%     4.44k ± 0%    ~     (p=0.867 n=10+10)
GetCIDRLabelsConcurrent/48-8        6.66k ± 0%     6.66k ± 0%    ~     (p=0.682 n=8+10)

Signed-off-by: Fabio Falzoi <fabio.falzoi@isovalent.com>
Signed-off-by: Fabio Falzoi <fabio.falzoi@isovalent.com>

pkg/labels/cidr/cidr.go

@@ -129,7 +129,7 @@ var (
 	mu lock.Mutex
 )
 
-const cidrLabelsCacheMaxSize = 16384
+const cidrLabelsCacheMaxSize = 8192
 
 var (
 	once sync.Once