327 research outputs found
Characterizing Service Level Objectives for Cloud Services: Motivation of Short-Term Cache Allocation Performance Modeling
Service level objectives (SLOs) stipulate performance goals for cloud applications, microservices, and infrastructure. SLOs are widely used, in part, because system managers can tailor goals to their products, companies, and workloads. Systems research intended to support strong SLOs should target realistic performance goals used by system managers in the field. Evaluations conducted with uncommon SLO goals may not translate to real systems. Some textbooks discuss the structure of SLOs but (1) they only sketch SLO goals and (2) they use outdated examples. We mined real SLOs published on the web, extracted their goals and characterized them. Many web documents discuss SLOs loosely but few provide details and reflect real settings. Systematic literature review (SLR) prunes results and reduces bias by (1) modeling expected SLO structure and (2) detecting and removing outliers. We collected 75 SLOs where response time, query percentile and reporting period were specified. We used these SLOs to confirm and refute common perceptions. For example, we found few SLOs with response time guarantees below 10 ms for 90% or more queries. This reality bolsters perceptions that single digit SLOs face fundamental research challenges.This work was funded by NSF Grants 1749501 and 1350941.No embargoAcademic Major: Computer Science and EngineeringAcademic Major: Financ
Immunopharmacology of ulipristal as an emergency contraceptive
A new progesterone antagonist, ulipristal has been made available as an emergency contraceptive. Ulipristal’s major mechanism of action as an emergency contraceptive has been ascribed to its ability to delay ovulation beyond the life span of the sperm. This paper analyzes the potential action of ulipristal (1) when unprotected intercourse and administration of ulipristal occur outside the fertility window and (2) when unprotected intercourse and administration of ulipristal occur at or within 24 hours of ovulation. When unprotected intercourse and the use of a single low dose of ulipristal occur outside of the fertility window, ulipristal behaves like a placebo. When unprotected intercourse and the use of a single low dose of ulipristal occur within the fertility window but before ovulation, ulipristal behaves like an emergency contraceptive by delaying ovulation and thereby preventing fertilization. When unprotected intercourse and the administration of ulipristal occur at or within 24 hours of ovulation, then ulipristal has an abortifacient action. It is proposed that the abortifacient mechanism of a low dose of ulipristal taken after fertilization but before implantation is due to the ability of ulipristal to block the maternal innate immune system to become immunotolerant to the paternal allogenic embryo. Progesterone’s critical immunotolerant actions involving early pregnancy factor, progesterone-induced blocking factor, and uterine natural killer cells are compromised by ulipristal
NetClone: Fast, Scalable, and Dynamic Request Cloning for Microsecond-Scale RPCs
Spawning duplicate requests, called cloning, is a powerful technique to
reduce tail latency by masking service-time variability. However, traditional
client-based cloning is static and harmful to performance under high load,
while a recent coordinator-based approach is slow and not scalable. Both
approaches are insufficient to serve modern microsecond-scale Remote Procedure
Calls (RPCs). To this end, we present NetClone, a request cloning system that
performs cloning decisions dynamically within nanoseconds at scale. Rather than
the client or the coordinator, NetClone performs request cloning in the network
switch by leveraging the capability of programmable switch ASICs. Specifically,
NetClone replicates requests based on server states and blocks redundant
responses using request fingerprints in the switch data plane. To realize the
idea while satisfying the strict hardware constraints, we address several
technical challenges when designing a custom switch data plane. NetClone can be
integrated with emerging in-network request schedulers like RackSched. We
implement a NetClone prototype with an Intel Tofino switch and a cluster of
commodity servers. Our experimental results show that NetClone can improve the
tail latency of microsecond-scale RPCs for synthetic and real-world application
workloads and is robust to various system conditions.Comment: 13 pages, ACM SIGCOMM 202
FEC killed the cut-through switch
Latency penalty in Ethernet links beyond 10Gb/s is due to
forward error correction (FEC) blocks. In the worst case a
single-hop penalty approaches the latency of an entire cutthrough
switch. Latency jitter is also introduced, making
latency prediction harder, with large peak to peak variance.
These factors stretch the tail of latency distribution in Rackscale
systems and Data Centers, which in turn degrades
performance of distributed applications. We analyse the underlying
mechanisms, calculate lower bounds and propose
a different approach that would reduce the penalty, allow
control over latency and feedback for application level optimisation.Rudin foundation, Isaac Newton trust, Leverhulme trust, Microsoft researc
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