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ABSTRACT: State-of-the-art high-performance processors like the IBM POWER5 and Intel i7 show a trend in industry towards on-chip Multiprocessors (CMP) involving Simultaneous Multithreading (SMT) in each core. In these processors, the way in which applications are assigned to cores plays a key role in the performance of each application and the overall system performance. In this paper we show that the system throughput highly depends on the Thread to Core Assignment (TCA), regardless the SMT Instruction Fetch (IFetch) Policy implemented in the cores. Our results indicate that a good TCA can improve the results of any underlying IFetch Policy, yielding speedups of up to 28%. Given the relevance of TCA, we propose an algorithm to manage it in CMP+SMT processors. The proposed throughput-oriented TCA Algorithm takes into account the workload characteristics and the underlying SMT IFetch Policy. Our results show that the TCA Algorithm obtains thread-to-core assignments 3% close to the optimal assignation for each case, yielding system throughput improvements up to 21%.
Computer Architecture and High Performance Computing, 2009. SBAC-PAD '09. 21st International Symposium on; 12/2009
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ABSTRACT: Different applications may exhibit radically different behaviors and thus have very different requirements in terms of hardware support. In simultaneous multithreading (SMT) architectures, the hardware is shared among multiple running applications in order to better profit from it. However, current architectures are designed for the common case, and try to satisfy a number of different application classes with a single design. That is, current designs are usually overdesigned for most cases, obtaining high performance, but wasting a lot of resources to do so. In this paper we present an alternative SMT architecture, the heterogeneously distributed SMT (hdSMT). Our architecture is based in a novel combination of SMT and clustering techniques in a heterogeneity-aware fashion. The hardware is designed to match the heterogeneous application behavior with the statically and heterogeneously partitioned resources. Such a design is aimed for minimizing the amount of resources wasted to achieve a given performance rate. On top of our statically partitioned architecture, we propose a heuristic policy to map threads to clusters so that each cluster matches the characteristics of the running threads and overall hardware usage is optimized. We compare our hdSMT architecture with a monolithic SMT processor, where all threads compete for the same resources, and with a homogeneous clustered SMT, where resources are statically and equally partitioned across clusters. Our results show that hdSMT architectures obtain an average improvement of 13% and 14% in optimizing performance per area over monolithic SMT and homogeneously clustered SMT respectively.
Parallel Processing, 2005. ICPP 2005. International Conference on; 07/2005
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ABSTRACT: A study was undertaken to assess the interactions between prenatal exposures, early life infections, atopic predisposition, and allergen exposures in the development of wheezing up to the age of 4 years in a tropical region of Africa.
The study subjects comprised children born at the district hospital in Ifakara, Tanzania during a 1 year period who were participating in a trial of iron supplementation and malaria chemoprophylaxis during the first year of life and followed for up to 4 years. From this group of subjects, 658 (79%) participated in the interview at 18 months and 528 (64%) in a second interview at 4 years. Wheezing was measured with the ISAAC questionnaire. A hospital based inpatient and outpatient surveillance system was set up to document all attendance by study children for any cause, including episodes of clinical malaria and lower respiratory tract infections. Total IgE levels and malaria parasites were measured in maternal and cord blood. Total IgE was also measured at 18 months of age. Indoor environmental levels of Der p I and Fel d I were determined using an enzyme linked immunosorbent assay at the same time as the interview at the age of 18 months.
The prevalence of wheezing at 4 years is common in Ifakara (14%, range 13-15%). The presence of malaria parasites in cord blood (odds ratio, OR = 6.84, 95% CI 1.84 to 24.0) and maternal asthma (OR = 8.47, 95% CI 2.72 to 26.2) were positively associated with wheezing at the age of 4 years, and cord blood total IgE was negatively associated (OR = 0.24, 95% CI 0.07 to 0.85) (all p<0.05). Parasitaemia at birth was not related to total IgE levels in cord blood (p=0.6). Clinical episodes of malaria during infancy were not associated with wheezing, and nor were levels of indoor aeroallergens.
These findings suggest that events occurring during pregnancy may play a role in the future appearance of wheezing, although the results must be interpreted with caution because of the small numbers studied.
Thorax 04/2001; 56(4):290-5. · 6.84 Impact Factor
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ABSTRACT: Atopy is consistently associated with asthma, except in a study in Africa. We assessed the association between atopy and asthma in women from a semirural area of Tanzania (East Africa).
All pregnant women delivering at the district hospital during a 1-year period were recruited (n = 658, 60.6% of those selected). Asthma was investigated by a standard questionnaire and atopy by specific IgE (immunoglobulin E) antibodies to Dermatophagoides pteronyssinus (Der p 1) and cockroach.
The prevalence of wheezing chest was 10.7%; of asthma, 3.5%. Levels of specific IgE of >0.35 kU/l (73%) and high levels of total IgE (62% higher than 1000 kU/l) were highly prevalent. Specific IgE antibody levels in sera were not associated with asthma (3.8% of women with negative specific IgE to any antigen had asthma in comparison to 4.0% of women with positive specific IgE; odds ratio [OR] = 1.06, 0.35-3.22). Total IgE was not different between women with asthma and women without asthma (P=0.36).
In tropical regions, the association between allergy and asthma is complex, and specific IgE reactivity to environmental allergens may not be related to asthma.
Allergy 08/2000; 55(8):762-6. · 6.27 Impact Factor
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D Schellenberg,
C Menendez,
E Kahigwa,
F Font,
C Galindo, C Acosta,
J A Schellenberg,
J J Aponte,
J Kimario,
H Urassa,
H Mshinda,
M Tanner,
P Alonso
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ABSTRACT: Malaria remains the most important parasitic cause of mortality in humans. Its presentation is thought to vary according to the intensity of Plasmodium falciparum transmission. However, detailed descriptions of presenting features and risk factors for death are only available from moderate transmission settings. Such descriptions help to improve case management and identify priority research areas. Standardized systematic procedures were used to collect clinical and laboratory data on 6,624 children admitted to hospital over a 1-year period in an intensely malarious part of Tanzania. Frequencies of signs and symptoms were calculated and their association with a fatal outcome was assessed using multivariate logistic regression. There were 72 deaths among 2,432 malaria cases (case fatality rate [CFR] = 3.0%); 44% of the cases and 54% of the deaths were in individuals less than 1 year of age. There was no association between level of parasitemia and CFR. Increased risk of dying was independently found in all children with hypoglycemia (odds ratio [OR] = 6.7, 95% confidence interval [CI] = 3.9-11.7), in children 1-7 months of age with tachypnea (OR = 8.8, 95% CI = 2.6-30.5) and dehydration (OR = 5.0, 95% CI = 1.9-14.2), and in children 8 months to 4 years of age with chest indrawing (OR = 4.7, 95% CI = 2.0-11.2) and inability to localize a painful stimulus (OR = 6.9, 95% CI = 2.9-16.5). Children in the bottom quartile of weight-for-age were more likely to die (OR = 2.1, 95% CI = 1.3-3.5). Eight percent of the malaria cases had severe anemia (packed cell volume < 15%) but 24% received a blood transfusion. The epidemiology of malaria disease may be more complex than previously thought. Improved case management in a wide variety of health facilities may result from adequate identification and treatment of dehydration and hypoglycemia. Transfusion-requiring anemia is a major problem and sustainable, effective preventive measures are urgently needed.
The American journal of tropical medicine and hygiene 10/1999; 61(3):431-8. · 2.59 Impact Factor
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C Menendez,
J M Sanchez-Tapias,
E Kahigwa,
H Mshinda,
J Costa,
J Vidal, C Acosta,
X Lopez-Labrador,
E Olmedo,
M Navia,
M Tanner,
J Rodes,
P L Alonso
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ABSTRACT: Hepatitis B and C markers were tested in 980 pregnant women, in the infants born to infected mothers, and in a random sample of 42 and 50, respectively, children born to uninfected mothers in Tanzania. Sixty-two women (6.3%) were positive for HBsAg and 15 (24%) were HBeAg-seropositive. Anti-HCV was detected in 49 women (5%), 15 (31%) of whom had detectable viremia. HCV RNA serum levels were low and only genotype 4 was identified. Sixty-six women (6.7%) were positive for anti-HIV, six of whom were coinfected with HBV and one with HCV. Anti-HEV was negative in the 180 women tested. At 8 months of age, HBsAg was detected in 8% and 2% of children born to HBV-infected and noninfected mothers, respectively (P = 0.2). Corresponding figures at 18 months of age were 31% and 21% (P = 0.3). When tested at 2 months of age, HCV RNA was not detected in any of the 43 children born to anti-HCV-positive mothers nor in any of 50 children born to anti-HCV-negative mothers. At 18 months, only one child, born to an anti-HCV-positive mother, had detectable HCV RNA. None of the infants born to women with HIV coinfection were infected with hepatitis viruses. This study suggests that exposure to HEV does not occur in southern Tanzania. The prevalence of current HBV infection in pregnant women from rural Tanzania is lower than in other sub-Saharan areas. In early childhood, HBV infection appears to occur by horizontal rather than maternofilial mechanisms of transmission. The prevalence of HCV infection is similar to that in other African countries. The results of this study show for the first time in Africa that mother-to-infant transmission does not play a significant role in the acquisition of HCV infection.
Journal of Medical Virology 08/1999; 58(3):215-20. · 2.82 Impact Factor
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ABSTRACT: BACKGROUND—A study was undertaken to assess the interactions between prenatal exposures, early life infections, atopic predisposition, and allergen exposures in the development of wheezing up to the age of 4 years in a tropical region of Africa.
METHODS—The study subjects comprised children born at the district hospital in Ifakara, Tanzania during a 1 year period who were participating in a trial of iron supplementation and malaria chemoprophylaxis during the first year of life and followed for up to 4 years. From this group of subjects, 658 (79%) participated in the interview at 18 months and 528 (64%) in a second interview at 4 years. Wheezing was measured with the ISAAC questionnaire. A hospital based inpatient and outpatient surveillance system was set up to document all attendance by study children for any cause, including episodes of clinical malaria and lower respiratory tract infections. Total IgE levels and malaria parasites were measured in maternal and cord blood. Total IgE was also measured at 18 months of age. Indoor environmental levels of Der p I and Fel d I were determined using an enzyme linked immunosorbent assay at the same time as the interview at the age of 18months.
RESULTS—The prevalence of wheezing at 4 years is common in Ifakara (14%, range 13-15%). The presence of malaria parasites in cord blood (odds ratio, OR = 6.84, 95% CI 1.84 to 24.0) and maternal asthma (OR = 8.47, 95% CI 2.72 to 26.2) were positively associated with wheezing at the age of 4 years, and cord blood total IgE was negatively associated (OR = 0.24, 95% CI 0.07 to 0.85) (all p<0.05). Parasitaemia at birth was not related to total IgE levels in cord blood (p=0.6). Clinical episodes of malaria during infancy were not associated with wheezing, and nor were levels of indoor aeroallergens.
CONCLUSION—These findings suggest that events occurring during pregnancy may play a role in the future appearance of wheezing, although the results must be interpreted with caution because of the small numbers studied.
