PNG  IHDRxsBIT|d pHYs+tEXtSoftwarewww.inkscape.org<,tEXtComment File Manager

File Manager

Path: /opt/golang/1.22.0/src/runtime/

Viewing File: histogram.go

// Copyright 2020 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package runtime

import (
	"runtime/internal/atomic"
	"runtime/internal/sys"
	"unsafe"
)

const (
	// For the time histogram type, we use an HDR histogram.
	// Values are placed in buckets based solely on the most
	// significant set bit. Thus, buckets are power-of-2 sized.
	// Values are then placed into sub-buckets based on the value of
	// the next timeHistSubBucketBits most significant bits. Thus,
	// sub-buckets are linear within a bucket.
	//
	// Therefore, the number of sub-buckets (timeHistNumSubBuckets)
	// defines the error. This error may be computed as
	// 1/timeHistNumSubBuckets*100%. For example, for 16 sub-buckets
	// per bucket the error is approximately 6%.
	//
	// The number of buckets (timeHistNumBuckets), on the
	// other hand, defines the range. To avoid producing a large number
	// of buckets that are close together, especially for small numbers
	// (e.g. 1, 2, 3, 4, 5 ns) that aren't very useful, timeHistNumBuckets
	// is defined in terms of the least significant bit (timeHistMinBucketBits)
	// that needs to be set before we start bucketing and the most
	// significant bit (timeHistMaxBucketBits) that we bucket before we just
	// dump it into a catch-all bucket.
	//
	// As an example, consider the configuration:
	//
	//    timeHistMinBucketBits = 9
	//    timeHistMaxBucketBits = 48
	//    timeHistSubBucketBits = 2
	//
	// Then:
	//
	//    011000001
	//    ^--
	//    │ ^
	//    │ └---- Next 2 bits -> sub-bucket 3
	//    └------- Bit 9 unset -> bucket 0
	//
	//    110000001
	//    ^--
	//    │ ^
	//    │ └---- Next 2 bits -> sub-bucket 2
	//    └------- Bit 9 set -> bucket 1
	//
	//    1000000010
	//    ^-- ^
	//    │ ^ └-- Lower bits ignored
	//    │ └---- Next 2 bits -> sub-bucket 0
	//    └------- Bit 10 set -> bucket 2
	//
	// Following this pattern, bucket 38 will have the bit 46 set. We don't
	// have any buckets for higher values, so we spill the rest into an overflow
	// bucket containing values of 2^47-1 nanoseconds or approx. 1 day or more.
	// This range is more than enough to handle durations produced by the runtime.
	timeHistMinBucketBits = 9
	timeHistMaxBucketBits = 48 // Note that this is exclusive; 1 higher than the actual range.
	timeHistSubBucketBits = 2
	timeHistNumSubBuckets = 1 << timeHistSubBucketBits
	timeHistNumBuckets    = timeHistMaxBucketBits - timeHistMinBucketBits + 1
	// Two extra buckets, one for underflow, one for overflow.
	timeHistTotalBuckets = timeHistNumBuckets*timeHistNumSubBuckets + 2
)

// timeHistogram represents a distribution of durations in
// nanoseconds.
//
// The accuracy and range of the histogram is defined by the
// timeHistSubBucketBits and timeHistNumBuckets constants.
//
// It is an HDR histogram with exponentially-distributed
// buckets and linearly distributed sub-buckets.
//
// The histogram is safe for concurrent reads and writes.
type timeHistogram struct {
	counts [timeHistNumBuckets * timeHistNumSubBuckets]atomic.Uint64

	// underflow counts all the times we got a negative duration
	// sample. Because of how time works on some platforms, it's
	// possible to measure negative durations. We could ignore them,
	// but we record them anyway because it's better to have some
	// signal that it's happening than just missing samples.
	underflow atomic.Uint64

	// overflow counts all the times we got a duration that exceeded
	// the range counts represents.
	overflow atomic.Uint64
}

// record adds the given duration to the distribution.
//
// Disallow preemptions and stack growths because this function
// may run in sensitive locations.
//
//go:nosplit
func (h *timeHistogram) record(duration int64) {
	// If the duration is negative, capture that in underflow.
	if duration < 0 {
		h.underflow.Add(1)
		return
	}
	// bucketBit is the target bit for the bucket which is usually the
	// highest 1 bit, but if we're less than the minimum, is the highest
	// 1 bit of the minimum (which will be zero in the duration).
	//
	// bucket is the bucket index, which is the bucketBit minus the
	// highest bit of the minimum, plus one to leave room for the catch-all
	// bucket for samples lower than the minimum.
	var bucketBit, bucket uint
	if l := sys.Len64(uint64(duration)); l < timeHistMinBucketBits {
		bucketBit = timeHistMinBucketBits
		bucket = 0 // bucketBit - timeHistMinBucketBits
	} else {
		bucketBit = uint(l)
		bucket = bucketBit - timeHistMinBucketBits + 1
	}
	// If the bucket we computed is greater than the number of buckets,
	// count that in overflow.
	if bucket >= timeHistNumBuckets {
		h.overflow.Add(1)
		return
	}
	// The sub-bucket index is just next timeHistSubBucketBits after the bucketBit.
	subBucket := uint(duration>>(bucketBit-1-timeHistSubBucketBits)) % timeHistNumSubBuckets
	h.counts[bucket*timeHistNumSubBuckets+subBucket].Add(1)
}

// write dumps the histogram to the passed metricValue as a float64 histogram.
func (h *timeHistogram) write(out *metricValue) {
	hist := out.float64HistOrInit(timeHistBuckets)
	// The bottom-most bucket, containing negative values, is tracked
	// separately as underflow, so fill that in manually and then iterate
	// over the rest.
	hist.counts[0] = h.underflow.Load()
	for i := range h.counts {
		hist.counts[i+1] = h.counts[i].Load()
	}
	hist.counts[len(hist.counts)-1] = h.overflow.Load()
}

const (
	fInf    = 0x7FF0000000000000
	fNegInf = 0xFFF0000000000000
)

func float64Inf() float64 {
	inf := uint64(fInf)
	return *(*float64)(unsafe.Pointer(&inf))
}

func float64NegInf() float64 {
	inf := uint64(fNegInf)
	return *(*float64)(unsafe.Pointer(&inf))
}

// timeHistogramMetricsBuckets generates a slice of boundaries for
// the timeHistogram. These boundaries are represented in seconds,
// not nanoseconds like the timeHistogram represents durations.
func timeHistogramMetricsBuckets() []float64 {
	b := make([]float64, timeHistTotalBuckets+1)
	// Underflow bucket.
	b[0] = float64NegInf()

	for j := 0; j < timeHistNumSubBuckets; j++ {
		// No bucket bit for the first few buckets. Just sub-bucket bits after the
		// min bucket bit.
		bucketNanos := uint64(j) << (timeHistMinBucketBits - 1 - timeHistSubBucketBits)
		// Convert nanoseconds to seconds via a division.
		// These values will all be exactly representable by a float64.
		b[j+1] = float64(bucketNanos) / 1e9
	}
	// Generate the rest of the buckets. It's easier to reason
	// about if we cut out the 0'th bucket.
	for i := timeHistMinBucketBits; i < timeHistMaxBucketBits; i++ {
		for j := 0; j < timeHistNumSubBuckets; j++ {
			// Set the bucket bit.
			bucketNanos := uint64(1) << (i - 1)
			// Set the sub-bucket bits.
			bucketNanos |= uint64(j) << (i - 1 - timeHistSubBucketBits)
			// The index for this bucket is going to be the (i+1)'th bucket
			// (note that we're starting from zero, but handled the first bucket
			// earlier, so we need to compensate), and the j'th sub bucket.
			// Add 1 because we left space for -Inf.
			bucketIndex := (i-timeHistMinBucketBits+1)*timeHistNumSubBuckets + j + 1
			// Convert nanoseconds to seconds via a division.
			// These values will all be exactly representable by a float64.
			b[bucketIndex] = float64(bucketNanos) / 1e9
		}
	}
	// Overflow bucket.
	b[len(b)-2] = float64(uint64(1)<<(timeHistMaxBucketBits-1)) / 1e9
	b[len(b)-1] = float64Inf()
	return b
}
b IDATxytVսϓ22 A@IR :hCiZ[v*E:WũZA ^dQeQ @ !jZ'>gsV仿$|?g)&x-EIENT ;@xT.i%-X}SvS5.r/UHz^_$-W"w)Ɗ/@Z &IoX P$K}JzX:;` &, ŋui,e6mX ԵrKb1ԗ)DADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADADA݀!I*]R;I2$eZ#ORZSrr6mteffu*((Pu'v{DIߔ4^pIm'77WEEE;vƎ4-$]'RI{\I&G :IHJ DWBB=\WR޽m o$K(V9ABB.}jѢv`^?IOȅ} ڶmG}T#FJ`56$-ھ}FI&v;0(h;Б38CӧOWf!;A i:F_m9s&|q%=#wZprrrla A &P\\СC[A#! {olF} `E2}MK/vV)i{4BffV\|ۭX`b@kɶ@%i$K z5zhmX[IXZ` 'b%$r5M4º/l ԃߖxhʔ)[@=} K6IM}^5k㏷݆z ΗÿO:gdGBmyT/@+Vɶ纽z񕏵l.y޴it뭷zV0[Y^>Wsqs}\/@$(T7f.InݺiR$푔n.~?H))\ZRW'Mo~v Ov6oԃxz! S,&xm/yɞԟ?'uaSѽb,8GלKboi&3t7Y,)JJ c[nzӳdE&KsZLӄ I?@&%ӟ۶mSMMњ0iؐSZ,|J+N ~,0A0!5%Q-YQQa3}$_vVrf9f?S8`zDADADADADADADADADAdqP,تmMmg1V?rSI꒟]u|l RCyEf٢9 jURbztѰ!m5~tGj2DhG*{H9)꒟ר3:(+3\?/;TUݭʴ~S6lڧUJ*i$d(#=Yݺd{,p|3B))q:vN0Y.jkק6;SɶVzHJJЀ-utѹսk>QUU\޲~]fFnK?&ߡ5b=z9)^|u_k-[y%ZNU6 7Mi:]ۦtk[n X(e6Bb."8cۭ|~teuuw|ήI-5"~Uk;ZicEmN/:]M> cQ^uiƞ??Ңpc#TUU3UakNwA`:Y_V-8.KKfRitv޲* 9S6ֿj,ՃNOMߤ]z^fOh|<>@Å5 _/Iu?{SY4hK/2]4%it5q]GGe2%iR| W&f*^]??vq[LgE_3f}Fxu~}qd-ږFxu~I N>\;͗O֊:̗WJ@BhW=y|GgwܷH_NY?)Tdi'?խwhlmQi !SUUsw4kӺe4rfxu-[nHtMFj}H_u~w>)oV}(T'ebʒv3_[+vn@Ȭ\S}ot}w=kHFnxg S 0eޢm~l}uqZfFoZuuEg `zt~? b;t%>WTkķh[2eG8LIWx,^\thrl^Ϊ{=dž<}qV@ ⠨Wy^LF_>0UkDuʫuCs$)Iv:IK;6ֲ4{^6եm+l3>݆uM 9u?>Zc }g~qhKwڭeFMM~pМuqǿz6Tb@8@Y|jx](^]gf}M"tG -w.@vOqh~/HII`S[l.6nØXL9vUcOoB\xoǤ'T&IǍQw_wpv[kmO{w~>#=P1Pɞa-we:iǏlHo׈꒟f9SzH?+shk%Fs:qVhqY`jvO'ρ?PyX3lх]˾uV{ݞ]1,MzYNW~̈́ joYn}ȚF߾׮mS]F z+EDxm/d{F{-W-4wY듏:??_gPf ^3ecg ҵs8R2מz@TANGj)}CNi/R~}c:5{!ZHӋӾ6}T]G]7W6^n 9*,YqOZj:P?Q DFL|?-^.Ɵ7}fFh׶xe2Pscz1&5\cn[=Vn[ĶE鎀uˌd3GII k;lNmشOuuRVfBE]ۣeӶu :X-[(er4~LHi6:Ѻ@ԅrST0trk%$Č0ez" *z"T/X9|8.C5Feg}CQ%͞ˣJvL/?j^h&9xF`њZ(&yF&Iݻfg#W;3^{Wo^4'vV[[K';+mӍִ]AC@W?1^{එyh +^]fm~iԵ]AB@WTk̏t uR?l.OIHiYyԶ]Aˀ7c:q}ힽaf6Z~қm(+sK4{^6}T*UUu]n.:kx{:2 _m=sAߤU@?Z-Vކеz왍Nэ{|5 pڶn b p-@sPg]0G7fy-M{GCF'%{4`=$-Ge\ eU:m+Zt'WjO!OAF@ik&t݆ϥ_ e}=]"Wz_.͜E3leWFih|t-wZۍ-uw=6YN{6|} |*={Ѽn.S.z1zjۻTH]흾 DuDvmvK.`V]yY~sI@t?/ϓ. m&["+P?MzovVЫG3-GRR[(!!\_,^%?v@ҵő m`Y)tem8GMx.))A]Y i`ViW`?^~!S#^+ѽGZj?Vģ0.))A꨷lzL*]OXrY`DBBLOj{-MH'ii-ϰ ok7^ )쭡b]UXSְmռY|5*cֽk0B7镹%ڽP#8nȎq}mJr23_>lE5$iwui+ H~F`IjƵ@q \ @#qG0".0" l`„.0! ,AQHN6qzkKJ#o;`Xv2>,tێJJ7Z/*A .@fفjMzkg @TvZH3Zxu6Ra'%O?/dQ5xYkU]Rֽkق@DaS^RSּ5|BeHNN͘p HvcYcC5:y #`οb;z2.!kr}gUWkyZn=f Pvsn3p~;4p˚=ē~NmI] ¾ 0lH[_L hsh_ғߤc_њec)g7VIZ5yrgk̞W#IjӪv>՞y睝M8[|]\շ8M6%|@PZڨI-m>=k='aiRo-x?>Q.}`Ȏ:Wsmu u > .@,&;+!!˱tﭧDQwRW\vF\~Q7>spYw$%A~;~}6¾ g&if_=j,v+UL1(tWake:@Ș>j$Gq2t7S?vL|]u/ .(0E6Mk6hiۺzښOrifޱxm/Gx> Lal%%~{lBsR4*}{0Z/tNIɚpV^#Lf:u@k#RSu =S^ZyuR/.@n&΃z~B=0eg뺆#,Þ[B/?H uUf7y Wy}Bwegל`Wh(||`l`.;Ws?V@"c:iɍL֯PGv6zctM̠':wuW;d=;EveD}9J@B(0iհ bvP1{\P&G7D޴Iy_$-Qjm~Yrr&]CDv%bh|Yzni_ˆR;kg}nJOIIwyuL}{ЌNj}:+3Y?:WJ/N+Rzd=hb;dj͒suݔ@NKMԄ jqzC5@y°hL m;*5ezᕏ=ep XL n?מ:r`۵tŤZ|1v`V뽧_csج'ߤ%oTuumk%%%h)uy]Nk[n 'b2 l.=͜E%gf$[c;s:V-͞WߤWh-j7]4=F-X]>ZLSi[Y*We;Zan(ӇW|e(HNNP5[= r4tP &0<pc#`vTNV GFqvTi*Tyam$ߏWyE*VJKMTfFw>'$-ؽ.Ho.8c"@DADADADADADADADADA~j*֘,N;Pi3599h=goضLgiJ5փy~}&Zd9p֚ e:|hL``b/d9p? fgg+%%hMgXosج, ΩOl0Zh=xdjLmhݻoO[g_l,8a]٭+ӧ0$I]c]:粹:Teꢢ"5a^Kgh,&= =՟^߶“ߢE ܹS J}I%:8 IDAT~,9/ʃPW'Mo}zNƍ쨓zPbNZ~^z=4mswg;5 Y~SVMRXUյڱRf?s:w ;6H:ºi5-maM&O3;1IKeamZh͛7+##v+c ~u~ca]GnF'ټL~PPPbn voC4R,ӟgg %hq}@#M4IÇ Oy^xMZx ) yOw@HkN˖-Sǎmb]X@n+i͖!++K3gd\$mt$^YfJ\8PRF)77Wא!Cl$i:@@_oG I{$# 8磌ŋ91A (Im7֭>}ߴJq7ޗt^ -[ԩSj*}%]&' -ɓ'ꫯVzzvB#;a 7@GxI{j޼ƌ.LÇWBB7`O"I$/@R @eee@۷>}0,ɒ2$53Xs|cS~rpTYYY} kHc %&k.], @ADADADADADADADADA@lT<%''*Lo^={رc5h %$+CnܸQ3fҥK}vUVVs9G R,_{xˇ3o߾;TTTd}馛]uuuG~iԩ@4bnvmvfϞ /Peeeq}}za I~,誫{UWW뮻}_~YƍSMMMYχ֝waw\ďcxꩧtEƍկ_?۷5@u?1kNׯWzz/wy>}zj3 k(ٺuq_Zvf̘:~ ABQ&r|!%KҥKgԞ={<_X-z !CyFUUz~ ABQIIIjݺW$UXXDٳZ~ ABQƍecW$<(~<RSSvZujjjԧOZQu@4 8m&&&jԩg$ď1h ͟?_{768@g =@`)))5o6m3)ѣƌJ;wҿUTT /KZR{~a=@0o<*狔iFɶ[ˎ;T]]OX@?K.ۈxN pppppppppppppppppPfl߾] ,{ァk۶mڿo5BTӦMӴiӴ|r DB2e|An!Dy'tkΝ[A $***t5' "!駟oaDnΝ:t֭[gDШQ06qD;@ x M6v(PiizmZ4ew"@̴ixf [~-Fٱc&IZ2|n!?$@{[HTɏ#@hȎI# _m(F /6Z3z'\r,r!;w2Z3j=~GY7"I$iI.p_"?pN`y DD?: _  Gÿab7J !Bx@0 Bo cG@`1C[@0G @`0C_u V1 aCX>W ` | `!<S `"<. `#c`?cAC4 ?c p#~@0?:08&_MQ1J h#?/`7;I  q 7a wQ A 1 Hp !#<8/#@1Ul7=S=K.4Z?E_$i@!1!E4?`P_  @Bă10#: "aU,xbFY1 [n|n #'vEH:`xb #vD4Y hi.i&EΖv#O H4IŶ}:Ikh @tZRF#(tXҙzZ ?I3l7q@õ|ۍ1,GpuY Ꮿ@hJv#xxk$ v#9 5 }_$c S#=+"K{F*m7`#%H:NRSp6I?sIՖ{Ap$I$I:QRv2$Z @UJ*$]<FO4IENDB`