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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,37 @@ | ||
| // 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. | ||
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| //go:build linux | ||
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| package discover | ||
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| import "github.com/thediveo/lxkns/model" | ||
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| // discoverAffinityScheduling discovers the CPU affinity lists and scheduler | ||
| // settings for the leader processes of all discovered namespaces. | ||
| func discoverAffinityScheduling(result *Result) { | ||
| if !result.Options.DiscoverAffinityScheduling { | ||
| return | ||
| } | ||
| for nstype := model.MountNS; nstype < model.NamespaceTypesCount; nstype++ { | ||
| for _, ns := range result.Namespaces[nstype] { | ||
| for _, leader := range ns.Leaders() { | ||
| if leader.Affinity != nil { | ||
| continue | ||
| } | ||
| _ = leader.RetrieveAffinityScheduling() | ||
| } | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,199 @@ | ||
| // 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. | ||
|
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| package model | ||
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| import ( | ||
| "sync/atomic" | ||
| "unsafe" | ||
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| "golang.org/x/sys/unix" | ||
| ) | ||
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| // CPUList is a list of CPU [from...to] ranges. CPU numbers are starting from | ||
| // zero. | ||
| type CPUList [][2]uint | ||
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| // CPUSet is a CPU bit string, such as used for CPU affinity masks. See also | ||
| // [sched_getaffinity(2)]. | ||
| // | ||
| // [sched_getaffinity(2)]: https://man7.org/linux/man-pages/man2/sched_getaffinity.2.html | ||
| type CPUSet []uint64 | ||
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| // The dynamically determined size of CPUSets on this system (size in uint64 | ||
| // words). This is usually smaller than the fixed-sized [unix.CPUSet] that Go's | ||
| // [unix.SchedGetaffinity] uses. | ||
| var setsize atomic.Uint64 | ||
| var wordbytesize = uint64(unsafe.Sizeof(CPUSet{0}[0])) | ||
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| func init() { | ||
| setsize.Store(1) | ||
| } | ||
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| // NewAffinityCPUList returns the affinity CPUList (list of CPU ranges) of the | ||
| // process with the passed PID. Otherwise, it returns an error. If pid is zero, | ||
| // then the affinity CPU list of the calling thread is returned (make sure to | ||
| // have the OS-level thread locked to the calling go routine in this case). | ||
| // | ||
| // Notes: | ||
| // - we don't use [unix.SchedGetaffinity] as this is tied to the fixed size | ||
| // [unix.CPUSet] type; instead, we dynamically figure out the size needed | ||
| // and cache the size internally. | ||
| // - retrieving the affinity CPU mask and then speed-running it to | ||
| // generate the range list is roughly two orders of magnitude faster than | ||
| // fetching “/proc/$PID/status” and looking for the “Cpus_allowed_list”, | ||
| // because generating the broad status procfs file is expensive. | ||
| func NewAffinityCPUList(pid PIDType) (CPUList, error) { | ||
| var set CPUSet | ||
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| setlenStart := setsize.Load() | ||
| setlen := setlenStart | ||
| for { | ||
| set = make([]uint64, setlen) | ||
| // see also: | ||
| // https://man7.org/linux/man-pages/man2/sched_setaffinity.2.html; we | ||
| // use RawSyscall here instead of Syscall as we know that | ||
| // SYS_SCHED_GETAFFINITY does not block, following Go's stdlib | ||
| // implementation. | ||
| _, _, e := unix.RawSyscall(unix.SYS_SCHED_GETAFFINITY, | ||
| uintptr(pid), uintptr(setlen*wordbytesize), uintptr(unsafe.Pointer(&set[0]))) | ||
| if e != 0 { | ||
| if e == unix.EINVAL { | ||
| setlen *= 2 | ||
| continue | ||
| } | ||
| return nil, e | ||
| } | ||
| // Set the new size; if this fails because another go routine already | ||
| // upped the set size, retry until we either notice that we're smaller | ||
| // than what was set as the new set size, or we succeed in setting the | ||
| // size. | ||
| for { | ||
| if setsize.CompareAndSwap(setlenStart, setlen) { | ||
| break | ||
| } | ||
| setlenStart = setsize.Load() | ||
| if setlenStart > setlen { | ||
| break | ||
| } | ||
| } | ||
| break | ||
| } | ||
| return set.NewCPUList(), nil | ||
| } | ||
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| // NewCPUList returns a list of CPU ranges for the given bitmap CPUSet. | ||
| // | ||
| // This is an optimized implementation that does not use any division and modulo | ||
| // operations; instead, it only uses increment and (single bit position) shift | ||
| // operations. Additionally, this implementation fast-forwards through all-0s | ||
| // and all-1s CPUSet words (uint64's). | ||
| func (s CPUSet) NewCPUList() CPUList { | ||
| setlen := uint64(len(s)) | ||
| cpulist := CPUList{} | ||
| cpuno := uint(0) | ||
| cpuwordidx := uint64(0) | ||
| cpuwordmask := uint64(1) | ||
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| findNextCPUInWord: | ||
| for { | ||
| // If we're inside a cpu mask word, try to find the next set cpu bit, if | ||
| // any, otherwise stop after we've fallen off the MSB end of the cpu | ||
| // mask word. | ||
| if cpuwordmask != 1 { | ||
| for { | ||
| if s[cpuwordidx]&cpuwordmask != 0 { | ||
| break | ||
| } | ||
| cpuno++ | ||
| cpuwordmask <<= 1 | ||
| if cpuwordmask == 0 { | ||
| // Oh no! We've fallen off the disc^Wcpu mask word. | ||
| cpuwordidx++ | ||
| cpuwordmask = 1 | ||
| break | ||
| } | ||
| } | ||
| } | ||
| // Try to fast-forward through completely unset cpu mask words, where | ||
| // possible. | ||
| for cpuwordidx < setlen && s[cpuwordidx] == 0 { | ||
| cpuno += 64 | ||
| cpuwordidx++ | ||
| } | ||
| if cpuwordidx >= setlen { | ||
| return cpulist | ||
| } | ||
| // We arrived at a non-zero cpu mask word, so let's now find the first | ||
| // cpu in it. | ||
| for { | ||
| if s[cpuwordidx]&cpuwordmask != 0 { | ||
| break | ||
| } | ||
| cpuno++ | ||
| cpuwordmask <<= 1 | ||
| } | ||
| // Hooray! We've finally located a CPU in use. Move on to the next CPU, | ||
| // handling a word boundary when necessary. | ||
| cpufrom := cpuno | ||
| cpuno++ | ||
| cpuwordmask <<= 1 | ||
| if cpuwordmask == 0 { | ||
| // Oh no! We've again fallen off the disc^Wcpu mask word. | ||
| cpuwordidx++ | ||
| cpuwordmask = 1 | ||
| } | ||
| // Now locate the next unset cpu within the currently inspected cpu mask | ||
| // word, until we find one or have exhausted our search within the | ||
| // current cpu mask word. | ||
| if cpuwordmask != 1 { | ||
| for { | ||
| if s[cpuwordidx]&cpuwordmask == 0 { | ||
| cpulist = append(cpulist, [2]uint{cpufrom, cpuno - 1}) | ||
| continue findNextCPUInWord | ||
| } | ||
| cpuno++ | ||
| cpuwordmask <<= 1 | ||
| if cpuwordmask == 0 { | ||
| cpuwordidx++ | ||
| cpuwordmask = 1 | ||
| break | ||
| } | ||
| } | ||
| } | ||
| // Try to fast-forward through completely set cpu mask words, where | ||
| // applicable. | ||
| for cpuwordidx < setlen && s[cpuwordidx] == ^uint64(0) { | ||
| cpuno += 64 | ||
| cpuwordidx++ | ||
| } | ||
| // Are we completely done? If so, add the final CPU span and then call | ||
| // it a day. | ||
| if cpuwordidx >= setlen { | ||
| cpulist = append(cpulist, [2]uint{cpufrom, cpuno - 1}) | ||
| return cpulist | ||
| } | ||
| // We arrived at a non-all-1s cpu mask word, so let's now find the first | ||
| // cpu in it that is unset. Add the CPU span, and then rinse and repeat | ||
| // from the beginning: find the next set CPU or fall off the disc. | ||
| for { | ||
| if s[cpuwordidx]&cpuwordmask == 0 { | ||
| cpulist = append(cpulist, [2]uint{cpufrom, cpuno - 1}) | ||
| break | ||
| } | ||
| cpuno++ | ||
| cpuwordmask <<= 1 | ||
| } | ||
| } | ||
| } |
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