A Linux Kernel Scheduler Implementation for Asymmetric CPUs

Την τελευταία δεκαετία έχουν χρησιμοποιηθεί ευρέως ασύμμετροι επεξεργαστές που αποτελούνται από πυρήνες διαφορετικών επεξεργαστικών δυνατοτήτων στις κινητές συσκευές. Η σχεδίαση τους επιτρέπει στους κατασκευαστές επεξεργαστών να προσφέρουν ελαττώσουν την κατανάλωση ενέργειας διατηρώντας καλή ταχύτητα. Ταυτοχρόνως, τέτοιοι επεξεργαστές απαιτούν ειδική μεταχείριση από τους προγραμματιστές λειτουργικών συστημάτων, οι οποίοι πρέπει να σχεδιάσουν ειδικούς χρονοπρογραμματιστές που να εκμεταλλεύονται την ασυμμετρία. Προσφάτως έχουν κυκλοφορήσει ασύμμετροι επεξεργαστές για προσωπικούς υπολογιστές, ένας χώρος στον οποίο παραδοσιακά κυριαρχούν οι συμμετρικοί επεξεργαστές. Αυτή η εξέλιξη είναι αποτέλεσμα της βελτιωμένου ενεργειακού τους προφίλ, καθώς και της χωρικής αποδοτικότητας αυτών των αρχιτεκτονικών. Η αντικατάσταση ενός μεγάλου πυρήνα με πολλούς μικρούς προσφέρει αυξημένη διεκπεραιωτική ικανότητα πολυνηματικών εργασιών χωρίς να αυξάνει το κόστος παραγωγής. Οι ασύμμετροι επεξεργαστές για υπολογιστές δημιουργούν μία σειρά από προβλήματα που οι χρονοπρογραμματιστές καλούνται να αντιμετωπίσουν. Η ανομοιογένεια στους υπολογιστές αποσκοπεί στον συνδυασμό της ελαχιστοποίησης της κατανάλωση ενέργειας σε καταστάσεις χαμηλού φόρτου και στη μακροχρόνια και ταχύ πολυνηματική απόδοση σε καταστάσεις αυξημένου φόρτου. Αντιθέτως, στις κινητές συσκευές, οι ανομοιογενής αρχιτεκτονικές αποσκοπούν στη μεγιστοποίηση της διάρκειας μπαταρίας, και την γοργή απόδοση σε σύντομα διαστήματα υψηλού φόρτου. Επιπλέον, η ταυτόχρονη πολυνημάτωση (SMT) είναι μία τεχνική που ενώ δεν χρησιμοποιείται σε κινητές συσκευές, χρησιμοποιείται από σχεδόν όλους τους επεξεργαστές υπολογιστών. Η κακή διαχείριση της ταυτόχρονης πολυνημάτωσης μπορεί να οδηγήσει σε σημαντική ελάττωση της αποδοτικότητας του συστήματος. Στην παρούσα πτυχιακή εργασία παρουσιάζουμε τον HCS, έναν γενικό χρονοπρογραμματιστή για ανομοιογενής επεξεργαστές που υποστηρίζουν ταυτόχρονη πολυνημάτωση. Συνδυάζει υπάρχουσες τεχνικές χρονοπρογραμματισμού ασύμμετρων επεξεργαστών για να προσφέρει ενεργειακή αποδοτικότητα και ταχύτητα. Επιπλέον, ο HCS είναι εύκολο να τροποποιηθεί από τους χρήστες ή τους προγραμματιστές εφαρμογών. Ο HCS εχει υλοποιηθεί, ως επέκταση του ULE, στον πυρήνα των Linux ως αντικαταστάτης του χρόνοπρογραμματιστή CFS.Asymmetric CPUs consisting of cores with different processing capacities have been widely used in mobile devices in the last decade. Their design allows chip-makers to offer improved energy efficiency while maintaining solid performance. The other side of the coin is that CPUs of this type require extra care from operating system developers, who have to design schedulers that take advantage of this asymmetry. Recently, heterogeneous (asymmetric) architectures have started to appear in the PC space, which has traditionally been dominated by homogeneous CPUs. In addition to the energy-efficiency benefits, this development is being propelled by the improved space-efficiency of small cores. Replacing a single big core with several small cores leads to increased multi-threaded performance without increasing manufacturing costs. Asymmetric Multi-Processing in computers poses some unique challenges that schedulers have to handle. Heterogeneity in computers aims for strong, sustained multithreaded performance in high-load situations and low power consumption in low-load situations. On the contrary, in mobile devices, heterogeneous architectures aim to maximize battery life while offering decent performance to a limited number of tasks with short bursts of CPU-intensive activity. Apart from that, Simultaneous Multi-threading hasn’t seen much use in mobile platforms leading to the design of heterogeneity-aware SMT-unaware schedulers. Mishandling SMT can lead to significant performance degradation and is unacceptable for a modern computer scheduler. In this thesis, we present HCS, a heterogeneity-aware, SMT-aware, general-purpose CPU scheduler for servers, desktops and laptops. It combines utilization-based, bias-based, and fairness-based scheduling schemes to provide efficiency and performance. To add to that, HCS allows both users and application developers to configure its behavior to better suit their needs. HCS is built on top of ULE and has been implemented in the Linux Kernel as a replacement for the energy-aware variant of the CFS scheduler

Facile CO Cleavage by a Multimetallic CsU2 Nitride Complex

Uranium nitrides are important materials with potential for application as fuels for nuclear power generation, and as highly active catalysts. Molecular nitride compounds could provide important insight into the nature of the uranium–nitride bond, but currently little is known about their reactivity. In this study, we found that a complex containing a nitride bridging two uranium centers and a cesium cation readily cleaved the C≡O bond (one of the strongest bonds in nature) under ambient conditions. The product formed has a [CsU2(μ-CN)(μ-O)] core, thus indicating that the three cations cooperate to cleave CO. Moreover, the addition of MeOTf to the nitride complex led to an exceptional valence disproportionation of the CsUIV–N–UIV core to yield CsUIII(OTf) and [MeN=UV] fragments. The important role of multimetallic cooperativity in both reactions is illustrated by the computed reaction mechanisms

NAČELO VLADAVINE PRAVA U TEORIJI I PRAKSI

Rad prikazuje temeljni i najviši ideal pravednog društva – načelo vladavine prava, kao i koncept ustavne vladavine. Tako rad prikazuje koncept ustavne vladavine kao sustav utemeljen na idejama vladavine prava i konstitucionalizma, definirajući ga kao pravni sustav pokoravanja zakonima, a ne ljudima. U radu se nastoji razgraničiti formalna od materijalne vladavine prava te se vladavina prava razmatra kao temeljna vrijednost u pravnim sustavima međunarodnih organizacija Ujedinjenih naroda, Europske unije i Vijeća Europe. Zaključno se prikazuju stajališta Ustavnog suda RH o načelu vladavine prava u konkretnim sudskim odlukama.The paper presents the fundamental and highest ideal of a fair society – the principle of the rule of law and the concept of constitutional rule. It depicts the concept of constitutional law as a system based on the ideas of the rule of law and constitutionalism, defining it as a law-abiding system. The paper attempts to separate the formal from the substantive rule of law and therein the rule of law is regarded as the fundamental value in the legal systems of international organizations such as the United Nations, the European Union and the Council of Europe. The conclusion shows the viewpoints of the Croatian Constitutional Court on the principle of the rule of law in concrete judgements

Terminal uranium(V/VI) nitride activation of carbon dioxide and carbon disulfide: factors governing diverse and well-defined cleavage and redox reactions

The reactivity of terminal uranium(V/VI) nitrides with CE2 (E=O, S) is presented. Well-defined C=E cleavage followed by zero-, one-, and two-electron redox events is observed. The uranium(V) nitride [U(TrenTIPS)(N)][K(B15C5)2] (1, TrenTIPS=N(CH2CH2NSiiPr3)3; B15C5=benzo-15-crown-5) reacts with CO2 to give [U(TrenTIPS)(O)(NCO)][K(B15C5)2] (3), whereas the uranium(VI) nitride [U(TrenTIPS)(N)] (2) reacts with CO2 to give isolable [U(TrenTIPS)(O)(NCO)] (4); complex 4 rapidly decomposes to known [U(TrenTIPS)(O)] (5) with concomitant formation of N2 and CO proposed, with the latter trapped as a vanadocene adduct. In contrast, 1 reacts with CS2 to give [U(TrenTIPS)(κ2-CS3)][K(B15C5)2] (6), 2, and [K(B15C5)2][NCS] (7), whereas 2 reacts with CS2 to give [U(TrenTIPS)(NCS)] (8) and “S”, with the latter trapped as Ph3PS. Calculated reaction profiles reveal outer-sphere reactivity for uranium(V) but inner-sphere mechanisms for uranium(VI); despite the wide divergence of products the initial activation of CE2 follows mechanistically related pathways, providing insight into the factors of uranium oxidation state, chalcogen, and NCE groups that govern the subsequent divergent redox reactions that include common one-electron reactions and a less-common two-electron redox event. Caution, we suggest, is warranted when utilising CS2 as a reactivity surrogate for CO2

Alkaline Earth-Centered CO Homologation, Reduction, and Amine Carbonylation

Reactions of β-diketiminato magnesium and calcium hydrides with 1 atm of CO result in a reductive coupling process to produce the corresponding derivatives of the <i>cis</i>-ethenediolate dianion. Computational (DFT) analysis of this process mediated by Ca, Sr, and Ba highlights a common mechanism and a facility for the reaction that is enhanced by increasing alkaline earth atomic weight. Reaction of CO with PhSiH₃ in the presence of the magnesium or calcium hydrides results in catalytic reduction to methylsilane and methylene silyl ether products, respectively. These reactions are proposed to ensue via the interception of initially formed group 2 formyl intermediates, an inference which is confirmed by a DFT analysis of the magnesium-centered reaction. The computational results identify the rate-determining process, requiring traversal of a 33.9 kcal mol^–1 barrier, as a Mg–H/C–O σ-bond metathesis reaction, associated with the ultimate cleavage of the C–O bond. The carbonylation reactivity is extended to a variety of magnesium and calcium amides. With primary amido complexes, which for calcium include a derivative of the parent [NH₂]⁻ anion, CO insertion is facile and ensues with subsequent nitrogen-to-carbon migration of hydrogen to yield a variety of dinuclear and, in one case, trinuclear formamidate species. The generation of initial carbenic carbamoyl intermediates is strongly implicated through the isolation of the CO insertion product of a magnesium <i>N</i>-methylanilide derivative. These observations are reinforced by a DFT analysis of the calcium-centered reaction with aniline, which confirms the exothermicity of the formamidate formation (Δ<i>H</i> = −67.7 kcal mol^–1). Stoichiometric reduction of the resultant magnesium and calcium formamidates with pinacolborane results in the synthesis of the corresponding <i>N</i>-borylated methylamines. This takes place via a sequence of reactions initiated through the generation of amidato­hydridoborate intermediates and a cascade of reactivity that is analogous to that previously reported for the deoxygenative hydroboration of organic isocyanates catalyzed by the same magnesium hydride precatalyst. Although a sequence of amine formylation and deoxygenation may be readily envisaged for the catalytic utilization of CO as a C₁ source in the production of methylamines, our observations demonstrate that competitive amine–borane dehydrocoupling is too facile under the conditions of 1 atm of CO employed

Two-Electron Reductive Carbonylation of Terminal Uranium(V) and Uranium(VI) Nitrides to Cyanate by Carbon Monoxide

Two-electron reductive carbonylation of the uranium(VI) nitride [U(TrenTIPS)(N)] (2, TrenTIPS=N(CH2CH2NSiiPr3)3) with CO gave the uranium(IV) cyanate [U(TrenTIPS)(NCO)] (3). KC8 reduction of 3 resulted in cyanate dissociation to give [U(TrenTIPS)] (4) and KNCO, or cyanate retention in [U(TrenTIPS)(NCO)][K(B15C5)2] (5, B15C5=benzo-15-crown-5 ether) with B15C5. Complexes 5 and 4 and KNCO were also prepared from CO and the uranium(V) nitride [{U(TrenTIPS)(N)K}2] (6), with or without B15C5, respectively. Complex 5 can be prepared directly from CO and [U(TrenTIPS)(N)][K(B15C5)2] (7). Notably, 7 reacts with CO much faster than 2. This unprecedented f-block reactivity was modeled theoretically, revealing nucleophilic attack of the π* orbital of CO by the nitride with activation energy barriers of 24.7 and 11.3 kcal mol−1 for uranium(VI) and uranium(V), respectively. A remarkably simple two-step, two-electron cycle for the conversion of azide to nitride to cyanate using 4, NaN3 and CO is presented

Mixed sandwich imido complexes of Uranium(V) and Uranium(IV): Synthesis, structure and redox behaviour

The mixed sandwich U(III) complex {U[η ^8 -C8H6(1,4-Si( iPr)3)2](Cp*)(THF)} reacts with the organic azides RN3 (R = SiMe3, 1-Ad, BMes2) to afford the corresponding, structurally characterised U(V) imido complexes {U[η ^8 -C8H6(1,4-Si( iPr)3)2](Cp*)(NR)}. In the case of R=SiMe3, the reducing power of the U(III) complex leads to reductive coupling as a parallel minor reaction pathway, forming R-R and the U(IV) azide-bridged complex{[U]}2(µ-N3)2, along with the expected [U]=NR complex. All three [U] =NR complexes show a quasi-reversible one electron reduction between -1.6 to -1.75 V, and for R= SiMe3, chemical reduction using K/Hg affords the anionic U(IV) complex K+ {U[η ^8 -C8H6(1,4-Si( iPr)3)2](Cp*)=NSiMe3} - . The molecular structure of the latter shows an extended structure in the solid state in which the K counter cations are successively sandwiched between the Cp* ligand of one [U] anion and the COTtips2 ligand of the next

Concomitant Carboxylate and Oxalate Formation From the Activation of CO2 by a Thorium(III) Complex

Improving our comprehension of diverse CO2 activation pathways is of vital importance for the widespread future utilization of this abundant greenhouse gas. CO2 activation by uranium(III) complexes is now relatively well understood, with oxo/carbonate formation predominating as CO2 is readily reduced to CO, but isolated thorium(III) CO2 activation is unprecedented. We show that the thorium(III) complex, [Th(Cp′′)3] (1, Cp′′={C5H3(SiMe3)2-1,3}), reacts with CO2 to give the mixed oxalate-carboxylate thorium(IV) complex [{Th(Cp′′)2[κ2-O2C{C5H3-3,3′-(SiMe3)2}]}2(μ-κ2:κ2-C2O4)] (3). The concomitant formation of oxalate and carboxylate is unique for CO2 activation, as in previous examples either reduction or insertion is favored to yield a single product. Therefore, thorium(III) CO2 activation can differ from better understood uranium(III) chemistry

On the Dehydrocoupling of Alkenylacetylenes Mediated by Various Samarocene Complexes: A Charming Story of Metal Cooperativity Revealing a Novel Dual Metal σ-Bond Metathesis Type of Mechanism (DM|σ-BM)

The prevailing reductive chemistry of Sm(II) has been accessed and explored mostly by the use of samarocene precursors. The highly reducing character of these congeners, along with their Lewis acidity and predominantly ionic bonding, allows for the relatively facile activation of C–H bonds, as well as peculiar transformations of unsaturated substrates (e.g., C–C couplings). Among other important C–C coupling reactions, the reaction of phenylacetylene with different mono- or bimetallic samarocene complexes affords trienediyl complexes of the type {[(C5Me5)2Sm]2(µ-η2:η2-PhC4Ph)}. In contrast, when t-butylacetylene is used, uncoupled monomers of the type (C5Me5)2Sm(C≡C–tBu) were obtained. Although this type of reactivity may appear to be simple, the mechanism underlying these transformations is complex. This conclusion is drawn from the density functional theory (DFT) mechanistic studies presented herein. The operating mechanistic paths consist of: (i) the oxidation of each samarium center and the concomitant double reduction of the alkyne to afford a binuclear intermediate; (ii) the C–H scission of the acetylinic bond that lies in between the two metals; (iii) a dual metal σ-bond metathesis (DM|σ-SBM) process that releases H2; and eventually (iv) the C–C coupling of the two bridged μ-alkynides to give the final bimetallic trienediyl complexes. For the latter mechanistic route, the experimentally used phenylacetylene was considered first as well as the aliphatic hex-1-yne. More interestingly, we shed light into the formation of the mono(alkynide) complex, being the final experimental product of the reaction with t-butylacetylene