On NoHit workloads gc is invoked for every load and since cache's goal
is to provide minimum slowdown the tracepoint overhead becomes visible.

Cache gc tracepoints were initially added for testing - to be able to
wait for gc to start/finish - when gc was running in its own goroutine,
but now, after 0e2be3b3 (X zodb/cache: Performing GC in separate
goroutine was actually a bad idea), when gc is running synchronously
there is need for this tracing events even from testing point of view.

So remove them.

---- 8< ----

name                        old time/op    new time/op    delta
NoopStorage                   57.9ns ± 1%    56.6ns ± 1%   -2.30%  (p=0.100 n=3+3)
NoopStorage-4                 57.4ns ± 1%    56.4ns ± 0%   -1.68%  (p=0.100 n=3+3)
CacheStartup                  2.13µs ±16%    1.95µs ± 2%     ~     (p=0.700 n=3+3)
CacheStartup-4                1.29µs ± 4%    1.31µs ± 5%     ~     (p=0.700 n=3+3)
CacheNoHit/size=0              677ns ± 1%     590ns ± 1%  -12.86%  (p=0.100 n=3+3)
CacheNoHit/size=0-4            664ns ± 1%     591ns ± 1%  -11.04%  (p=0.100 n=3+3)
CacheNoHit/size=16             792ns ± 0%     707ns ± 0%  -10.81%  (p=0.100 n=3+3)
CacheNoHit/size=16-4           788ns ± 0%     711ns ± 1%   -9.85%  (p=0.100 n=3+3)
CacheNoHit/size=128            796ns ± 0%     717ns ± 0%   -9.93%  (p=0.100 n=3+3)
CacheNoHit/size=128-4          795ns ± 1%     716ns ± 0%   -9.86%  (p=0.100 n=3+3)
CacheNoHit/size=512            816ns ± 0%     737ns ± 0%   -9.69%  (p=0.100 n=3+3)
CacheNoHit/size=512-4          803ns ± 0%     721ns ± 0%  -10.25%  (p=0.100 n=3+3)
CacheNoHit/size=4096          1.05µs ± 1%    0.95µs ± 1%  -10.13%  (p=0.100 n=3+3)
CacheNoHit/size=4096-4         856ns ± 0%     780ns ± 1%   -8.91%  (p=0.100 n=3+3)
CacheHit/size=0                664ns ± 0%     589ns ± 1%  -11.34%  (p=0.100 n=3+3)
CacheHit/size=0-4              660ns ± 0%     588ns ± 0%  -10.86%  (p=0.100 n=3+3)
CacheHit/size=16               123ns ± 4%     122ns ± 1%     ~     (p=0.800 n=3+3)
CacheHit/size=16-4             121ns ± 1%     123ns ± 1%     ~     (p=0.300 n=3+3)
CacheHit/size=128              124ns ± 1%     127ns ± 2%   +2.70%  (p=0.100 n=3+3)
CacheHit/size=128-4            124ns ± 1%     126ns ± 1%   +2.16%  (p=0.100 n=3+3)
CacheHit/size=512              126ns ± 1%     128ns ± 2%     ~     (p=0.400 n=3+3)
CacheHit/size=512-4            125ns ± 1%     127ns ± 1%   +1.60%  (p=0.100 n=3+3)
CacheHit/size=4096             127ns ± 1%     130ns ± 0%   +2.09%  (p=0.100 n=3+3)
CacheHit/size=4096-4           128ns ± 1%     130ns ± 1%   +1.56%  (p=0.100 n=3+3)
NoopStoragePar                59.2ns ± 1%    59.7ns ± 3%     ~     (p=1.000 n=3+3)
NoopStoragePar-4              31.2ns ± 8%    31.3ns ± 8%     ~     (p=1.000 n=3+3)
CacheStartupPar               2.04µs ± 6%    1.97µs ±13%     ~     (p=1.000 n=3+3)
CacheStartupPar-4             1.48µs ± 3%    1.49µs ± 4%     ~     (p=0.700 n=3+3)
CacheNoHitPar/size=0           670ns ± 0%     591ns ± 0%  -11.75%  (p=0.100 n=3+3)
CacheNoHitPar/size=0-4         904ns ± 0%     811ns ± 0%  -10.32%  (p=0.100 n=3+3)
CacheNoHitPar/size=16          789ns ± 0%     713ns ± 0%   -9.63%  (p=0.100 n=3+3)
CacheNoHitPar/size=16-4       1.03µs ± 0%    0.92µs ± 0%  -10.06%  (p=0.100 n=3+3)
CacheNoHitPar/size=128         800ns ± 0%     717ns ± 0%  -10.45%  (p=0.100 n=3+3)
CacheNoHitPar/size=128-4      1.04µs ± 0%    0.95µs ± 0%   -8.63%  (p=0.100 n=3+3)
CacheNoHitPar/size=512         818ns ± 0%     733ns ± 0%  -10.35%  (p=0.100 n=3+3)
CacheNoHitPar/size=512-4      1.07µs ± 0%    0.97µs ± 0%   -9.04%  (p=0.100 n=3+3)
CacheNoHitPar/size=4096       1.06µs ± 1%    0.94µs ± 0%  -11.50%  (p=0.100 n=3+3)
CacheNoHitPar/size=4096-4     1.17µs ± 1%    1.07µs ± 0%   -7.89%  (p=0.100 n=3+3)
CacheHitPar/size=0             665ns ± 0%     587ns ± 0%  -11.69%  (p=0.100 n=3+3)
CacheHitPar/size=0-4           903ns ± 1%     805ns ± 0%  -10.85%  (p=0.100 n=3+3)
CacheHitPar/size=16            124ns ± 1%     122ns ± 1%     ~     (p=0.200 n=3+3)
CacheHitPar/size=16-4          217ns ± 1%     236ns ± 1%   +8.74%  (p=0.100 n=3+3)
CacheHitPar/size=128           125ns ± 0%     125ns ± 1%     ~     (p=1.000 n=3+3)
CacheHitPar/size=128-4         215ns ± 1%     220ns ± 0%   +2.48%  (p=0.100 n=3+3)
CacheHitPar/size=512           127ns ± 1%     127ns ± 2%     ~     (p=0.600 n=3+3)
CacheHitPar/size=512-4         241ns ± 0%     219ns ± 0%   -9.14%  (p=0.100 n=3+3)
CacheHitPar/size=4096          129ns ± 0%     129ns ± 1%     ~     (p=1.000 n=3+3)
CacheHitPar/size=4096-4        236ns ± 4%     223ns ± 5%     ~     (p=0.200 n=3+3)
NoopStorageProc               56.1ns ± 0%    54.7ns ± 0%   -2.44%  (p=0.100 n=3+3)
NoopStorageProc-4             37.1ns ±10%    31.8ns ± 4%  -14.45%  (p=0.100 n=3+3)
CacheStartupProc              1.79µs ± 3%    1.88µs ±11%     ~     (p=0.700 n=3+3)
CacheStartupProc-4            1.08µs ± 7%    1.13µs ± 3%     ~     (p=0.400 n=3+3)
CacheNoHitProc/size=0          669ns ± 0%     598ns ± 0%  -10.66%  (p=0.100 n=3+3)
CacheNoHitProc/size=0-4        414ns ±15%     309ns ± 0%  -25.38%  (p=0.100 n=3+3)
CacheNoHitProc/size=16         792ns ± 0%     711ns ± 0%  -10.27%  (p=0.100 n=3+3)
CacheNoHitProc/size=16-4       440ns ± 7%     356ns ± 0%  -19.02%  (p=0.100 n=3+3)
CacheNoHitProc/size=128        808ns ± 0%     722ns ± 1%  -10.61%  (p=0.100 n=3+3)
CacheNoHitProc/size=128-4      467ns ± 8%     363ns ± 0%  -22.29%  (p=0.100 n=3+3)
CacheNoHitProc/size=512        834ns ± 1%     741ns ± 1%  -11.08%  (p=0.100 n=3+3)
CacheNoHitProc/size=512-4      499ns ± 9%     394ns ± 0%  -20.98%  (p=0.100 n=3+3)
CacheNoHitProc/size=4096      1.07µs ± 0%    0.94µs ± 0%  -11.71%  (p=0.100 n=3+3)
CacheNoHitProc/size=4096-4     629ns ± 3%     565ns ± 0%  -10.12%  (p=0.100 n=3+3)
CacheHitProc/size=0            669ns ± 0%     598ns ± 0%  -10.61%  (p=0.100 n=3+3)
CacheHitProc/size=0-4          381ns ± 2%     310ns ± 0%  -18.72%  (p=0.100 n=3+3)
CacheHitProc/size=16           121ns ± 1%     120ns ± 1%     ~     (p=0.400 n=3+3)
CacheHitProc/size=16-4        65.0ns ± 3%    57.5ns ± 2%  -11.59%  (p=0.100 n=3+3)
CacheHitProc/size=128          124ns ± 0%     123ns ± 1%     ~     (p=0.700 n=3+3)
CacheHitProc/size=128-4       74.9ns ± 3%    58.1ns ± 0%  -22.44%  (p=0.100 n=3+3)
CacheHitProc/size=512          125ns ± 1%     126ns ± 2%     ~     (p=0.600 n=3+3)
CacheHitProc/size=512-4       71.5ns ± 2%    58.6ns ± 0%  -17.96%  (p=0.100 n=3+3)
CacheHitProc/size=4096         132ns ± 6%     128ns ± 1%     ~     (p=0.600 n=3+3)
CacheHitProc/size=4096-4      80.5ns ± 7%    69.8ns ± 0%  -13.30%  (p=0.100 n=3+3)

name                        old alloc/op   new alloc/op   delta
NoopStorage                    0.00B          0.00B          ~     (all equal)
NoopStorage-4                  0.00B          0.00B          ~     (all equal)
CacheStartup                    285B ± 0%      285B ± 0%     ~     (all equal)
CacheStartup-4                  285B ± 0%      285B ± 0%     ~     (all equal)
CacheNoHit/size=0               152B ± 0%      152B ± 0%     ~     (all equal)
CacheNoHit/size=0-4             152B ± 0%      152B ± 0%     ~     (all equal)
CacheNoHit/size=16              153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHit/size=16-4            153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHit/size=128             153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHit/size=128-4           153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHit/size=512             153B ± 0%      153B ± 0%     ~     (p=1.000 n=3+3)
CacheNoHit/size=512-4           153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHit/size=4096            153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHit/size=4096-4          152B ± 0%      153B ± 0%     ~     (p=1.000 n=3+3)
CacheHit/size=0                 152B ± 0%      152B ± 0%     ~     (all equal)
CacheHit/size=0-4               152B ± 0%      152B ± 0%     ~     (all equal)
CacheHit/size=16               0.00B          0.00B          ~     (all equal)
CacheHit/size=16-4             0.00B          0.00B          ~     (all equal)
CacheHit/size=128              0.00B          0.00B          ~     (all equal)
CacheHit/size=128-4            0.00B          0.00B          ~     (all equal)
CacheHit/size=512              0.00B          0.00B          ~     (all equal)
CacheHit/size=512-4            0.00B          0.00B          ~     (all equal)
CacheHit/size=4096             0.00B          0.00B          ~     (all equal)
CacheHit/size=4096-4           0.00B          0.00B          ~     (all equal)
NoopStoragePar                 0.00B          0.00B          ~     (all equal)
NoopStoragePar-4               0.00B          0.00B          ~     (all equal)
CacheStartupPar                 285B ± 0%      285B ± 0%     ~     (all equal)
CacheStartupPar-4               281B ± 0%      282B ± 0%     ~     (p=0.300 n=3+3)
CacheNoHitPar/size=0            152B ± 0%      152B ± 0%     ~     (all equal)
CacheNoHitPar/size=0-4          152B ± 0%      152B ± 0%     ~     (all equal)
CacheNoHitPar/size=16           153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitPar/size=16-4         155B ± 0%      154B ± 0%     ~     (p=0.400 n=3+3)
CacheNoHitPar/size=128          153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitPar/size=128-4        153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitPar/size=512          153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitPar/size=512-4        153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitPar/size=4096         153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitPar/size=4096-4       153B ± 0%      153B ± 0%     ~     (all equal)
CacheHitPar/size=0              152B ± 0%      152B ± 0%     ~     (all equal)
CacheHitPar/size=0-4            152B ± 0%      152B ± 0%     ~     (all equal)
CacheHitPar/size=16            0.00B          0.00B          ~     (all equal)
CacheHitPar/size=16-4          0.00B          0.00B          ~     (all equal)
CacheHitPar/size=128           0.00B          0.00B          ~     (all equal)
CacheHitPar/size=128-4         0.00B          0.00B          ~     (all equal)
CacheHitPar/size=512           0.00B          0.00B          ~     (all equal)
CacheHitPar/size=512-4         0.00B          0.00B          ~     (all equal)
CacheHitPar/size=4096          0.00B          0.00B          ~     (all equal)
CacheHitPar/size=4096-4        0.00B          0.00B          ~     (all equal)
NoopStorageProc                0.00B          0.00B          ~     (all equal)
NoopStorageProc-4              0.00B          0.00B          ~     (all equal)
CacheStartupProc                285B ± 0%      285B ± 0%     ~     (all equal)
CacheStartupProc-4              285B ± 0%      285B ± 0%     ~     (all equal)
CacheNoHitProc/size=0           152B ± 0%      152B ± 0%     ~     (all equal)
CacheNoHitProc/size=0-4         152B ± 0%      152B ± 0%     ~     (all equal)
CacheNoHitProc/size=16          153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitProc/size=16-4        153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitProc/size=128         153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitProc/size=128-4       153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitProc/size=512         153B ± 0%      153B ± 0%     ~     (p=1.000 n=3+3)
CacheNoHitProc/size=512-4       153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitProc/size=4096        153B ± 0%      153B ± 0%     ~     (all equal)
CacheNoHitProc/size=4096-4      153B ± 0%      153B ± 0%     ~     (all equal)
CacheHitProc/size=0             152B ± 0%      152B ± 0%     ~     (all equal)
CacheHitProc/size=0-4           152B ± 0%      152B ± 0%     ~     (all equal)
CacheHitProc/size=16           0.00B          0.00B          ~     (all equal)
CacheHitProc/size=16-4         0.00B          0.00B          ~     (all equal)
CacheHitProc/size=128          0.00B          0.00B          ~     (all equal)
CacheHitProc/size=128-4        0.00B          0.00B          ~     (all equal)
CacheHitProc/size=512          0.00B          0.00B          ~     (all equal)
CacheHitProc/size=512-4        0.00B          0.00B          ~     (all equal)
CacheHitProc/size=4096         0.00B          0.00B          ~     (all equal)
CacheHitProc/size=4096-4       0.00B          0.00B          ~     (all equal)

name                        old allocs/op  new allocs/op  delta
NoopStorage                     0.00           0.00          ~     (all equal)
NoopStorage-4                   0.00           0.00          ~     (all equal)
CacheStartup                    5.00 ± 0%      5.00 ± 0%     ~     (all equal)
CacheStartup-4                  5.00 ± 0%      5.00 ± 0%     ~     (all equal)
CacheNoHit/size=0               3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=0-4             3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=16              3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=16-4            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=128             3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=128-4           3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=512             3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=512-4           3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=4096            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHit/size=4096-4          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHit/size=0                 3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHit/size=0-4               3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHit/size=16                0.00           0.00          ~     (all equal)
CacheHit/size=16-4              0.00           0.00          ~     (all equal)
CacheHit/size=128               0.00           0.00          ~     (all equal)
CacheHit/size=128-4             0.00           0.00          ~     (all equal)
CacheHit/size=512               0.00           0.00          ~     (all equal)
CacheHit/size=512-4             0.00           0.00          ~     (all equal)
CacheHit/size=4096              0.00           0.00          ~     (all equal)
CacheHit/size=4096-4            0.00           0.00          ~     (all equal)
NoopStoragePar                  0.00           0.00          ~     (all equal)
NoopStoragePar-4                0.00           0.00          ~     (all equal)
CacheStartupPar                 5.00 ± 0%      5.00 ± 0%     ~     (all equal)
CacheStartupPar-4               4.00 ± 0%      4.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=0            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=0-4          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=16           3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=16-4         3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=128          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=128-4        3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=512          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=512-4        3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=4096         3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitPar/size=4096-4       3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHitPar/size=0              3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHitPar/size=0-4            3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHitPar/size=16             0.00           0.00          ~     (all equal)
CacheHitPar/size=16-4           0.00           0.00          ~     (all equal)
CacheHitPar/size=128            0.00           0.00          ~     (all equal)
CacheHitPar/size=128-4          0.00           0.00          ~     (all equal)
CacheHitPar/size=512            0.00           0.00          ~     (all equal)
CacheHitPar/size=512-4          0.00           0.00          ~     (all equal)
CacheHitPar/size=4096           0.00           0.00          ~     (all equal)
CacheHitPar/size=4096-4         0.00           0.00          ~     (all equal)
NoopStorageProc                 0.00           0.00          ~     (all equal)
NoopStorageProc-4               0.00           0.00          ~     (all equal)
CacheStartupProc                5.00 ± 0%      5.00 ± 0%     ~     (all equal)
CacheStartupProc-4              5.00 ± 0%      5.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=0           3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=0-4         3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=16          3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=16-4        3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=128         3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=128-4       3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=512         3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=512-4       3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=4096        3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheNoHitProc/size=4096-4      3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHitProc/size=0             3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHitProc/size=0-4           3.00 ± 0%      3.00 ± 0%     ~     (all equal)
CacheHitProc/size=16            0.00           0.00          ~     (all equal)
CacheHitProc/size=16-4          0.00           0.00          ~     (all equal)
CacheHitProc/size=128           0.00           0.00          ~     (all equal)
CacheHitProc/size=128-4         0.00           0.00          ~     (all equal)
CacheHitProc/size=512           0.00           0.00          ~     (all equal)
CacheHitProc/size=512-4         0.00           0.00          ~     (all equal)
CacheHitProc/size=4096          0.00           0.00          ~     (all equal)
CacheHitProc/size=4096-4        0.00           0.00          ~     (all equal)