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Merge pull request #51 from thediveo/develop
feat: affinity; refact: SortProcessByX
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,83 @@ | ||
| // Copyright 2024 Harald Albrecht. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); you may not | ||
| // use this file except in compliance with the License. You may obtain a copy | ||
| // of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| // License for the specific language governing permissions and limitations | ||
| // under the License. | ||
|
|
||
| package model | ||
|
|
||
| import ( | ||
| "os" | ||
| "strconv" | ||
| "strings" | ||
| ) | ||
|
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| // SortProcessByPID sorts processes by increasing PID numbers (no interval | ||
| // arithmetics though). | ||
| func SortProcessByPID(a, b *Process) int { | ||
| return int(a.PID) - int(b.PID) | ||
| } | ||
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| // SortProcessByAgeThenPIDDistance sorts processes first by their “age” | ||
| // (starttime) and then by their PIDs, taking PID number wrap-arounds into | ||
| // consideration. | ||
| // | ||
| // As PIDs are monotonously increasing, wrapping around at “N” (which defaults | ||
| // to 1<<22 on Linux 64 bit systems), we consider a PID “B” to be after PID “A” | ||
| // if the “positive” distance from “A” to “B” (in increasing PIDs, distance | ||
| // taken modulo N) is at most N/2. | ||
| // | ||
| // For a nice write-up see also [The ryg blog: Intervals in modular arithmetic]. | ||
| // | ||
| // [The ryg blog: Intervals in modular arithmetic]: https://fgiesen.wordpress.com/2015/09/24/intervals-in-modular-arithmetic/ | ||
| func SortProcessByAgeThenPIDDistance(a, b *Process) int { | ||
| switch { | ||
| case a.Starttime < b.Starttime: | ||
| return -1 | ||
| case a.Starttime > b.Starttime: | ||
| return 1 | ||
| } | ||
| pidA := uint64(a.PID) | ||
| pidB := uint64(b.PID) | ||
| switch dist := (pidB - pidA) & pidMaxMask; { | ||
| case dist == 0: | ||
| return 0 | ||
| case dist <= pidMaxDist: | ||
| return -1 | ||
| default: | ||
| return 1 | ||
| } | ||
| } | ||
|
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| var pidMaxMask uint64 // N-1 | ||
| var pidMaxDist uint64 // N/2 | ||
|
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| // pidWrapping reads the PID interval “N” set for this system (which must be to | ||
| // the power of two) and then returns N-1 and N/2, falling back to the specified | ||
| // default N in case the system configuration cannot be read. | ||
| func pidWrapping(defaultMax uint64) (mask, maxdist uint64) { | ||
| mask = defaultMax - 1 | ||
| maxdist = defaultMax >> 1 | ||
| // https://www.man7.org/linux/man-pages/man5/proc_sys_kernel.5.html | ||
| pidmaxb, err := os.ReadFile("/proc/sys/kernel/pid_max") | ||
| if err != nil { | ||
| return | ||
| } | ||
| pidmax, err := strconv.ParseUint(strings.TrimSuffix(string(pidmaxb), "\n"), 10, 32) | ||
| if err != nil { | ||
| return | ||
| } | ||
| return pidmax - 1, pidmax >> 1 | ||
| } | ||
|
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| func init() { | ||
| pidMaxMask, pidMaxDist = pidWrapping((uint64(1) << 22)) | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,61 @@ | ||
| // Copyright 2024 Harald Albrecht. | ||
| // | ||
| // Licensed under the Apache License, Version 2.0 (the "License"); you may not | ||
| // use this file except in compliance with the License. You may obtain a copy | ||
| // of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, software | ||
| // distributed under the License is distributed on an "AS IS" BASIS, WITHOUT | ||
| // WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the | ||
| // License for the specific language governing permissions and limitations | ||
| // under the License. | ||
|
|
||
| package model | ||
|
|
||
| import ( | ||
| deco "github.com/onsi/ginkgo/v2/dsl/decorators" | ||
|
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| . "github.com/onsi/ginkgo/v2/dsl/core" | ||
| . "github.com/onsi/ginkgo/v2/dsl/table" | ||
| . "github.com/onsi/gomega" | ||
| ) | ||
|
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| var _ = Describe("Mr Wehrli sorting processes", func() { | ||
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| It("detects the system's PID wrap-around", func() { | ||
| mask, dist := pidWrapping(0) | ||
| Expect(mask).NotTo(BeZero()) | ||
| Expect(dist).NotTo(BeZero()) | ||
| Expect((dist << 1) - 1).To(Equal(mask)) | ||
| }) | ||
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| Context("interval arithmetic", deco.Ordered, func() { | ||
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| BeforeAll(func() { | ||
| pidMaxMask, pidMaxDist = 8-1, 8>>1 | ||
| DeferCleanup(func() { | ||
| pidMaxMask, pidMaxDist = pidWrapping((uint64(1) << 22)) | ||
| }) | ||
| }) | ||
|
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| DescribeTable("sorting by age and PID distance", | ||
| func(ageA int, pidA int, ageB int, pidB int, expect int) { | ||
| delta := SortProcessByAgeThenPIDDistance( | ||
| &Process{PID: PIDType(pidA), ProTaskCommon: ProTaskCommon{Starttime: uint64(ageA)}}, | ||
| &Process{PID: PIDType(pidB), ProTaskCommon: ProTaskCommon{Starttime: uint64(ageB)}}) | ||
| Expect(delta).To(Equal(expect), | ||
| "(%d-%d)&%x=%x ?? %x", pidA, pidB, pidMaxMask, (pidB-pidA)&int(pidMaxMask), pidMaxDist) | ||
| }, | ||
| Entry("a older than b", 100, 1, 200, 2, -1), | ||
| Entry("a younger than b", 200, 1, 100, 2, 1), | ||
| Entry("a same age as b, PID a before PID b, nowrap", 100, 4, 100, 5, -1), | ||
| Entry("a same age as b, PID b before PID a, nowrap", 100, 5, 100, 4, 1), | ||
| Entry("a same age as b, PID a before PID b, wrap", 100, 7, 100, 1, -1), | ||
| Entry("a same age as b, PID b before PID a, wrap", 100, 1, 100, 7, 1), | ||
| ) | ||
|
|
||
| }) | ||
|
|
||
| }) |
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