تستخدم تقنية الحجز المسبق لضمان تزويد الموارد عند الطلب للأنواع المختلفة من التطبيقات و منها دفق الأعمال. ما زالت هذه التقنية مثار جدل واسع في المجتمع البحثي و الأعمال لإمكانيتها تخفيض استغلالية الموارد. قُدمت عدة حلول لتحسين استغلالية الموارد تحت الحجز المسبق عن طريق توليد حجوزات مرنة و قابلة للتعديل من قبل الإدارة المحلية للموارد، مما يمكنها من تحسين استغلالية مواردها و خفض التجزئة الداخلية فيها. تعمل موّلدات مخططات الحجز المرن على تحويل المهمات ذات الحجز المسبق
القاسي، التي تعد من أصعب أنواع الحجز، إلى مهمات ذات حجز مسبق مرتخ، أو مرن؛ و لكن تعتمد معظم الأعمال المقدمة في هذا المجال على إضافة زمن محدد إلى طول المجدول الناتج، و من ثم توزيع هذا الزمن على المهمات المشكلة للدفق.
تقدم هذه الورقة خوارزمية جديدة مستقلة لتوليد مخطط حجز مسبق مرن لمهمات دفق الأعمال دون أية إضافات زمنية؛ بل تعتمد على الاستغلال الأمثلي للفجوات الزمنية الموجودة في مجدولات دفق الأعمال. تستخدم هذه الخوارزمية تقنية استطلاع الفجوات الزمنية في المجدول الناتج، و لكنها تضيف إليها و تعدلها لتستعمل مع تخطيط الحجز المرن. أظهرت نتائج اختبار هذه الخوارزمية تقدمها على الخوارزميات الأخرى الموجودة في هذا المجال بمقدار حد أدنى يقارب 25 %؛ و هي تقدم بذلك حلولاً كفوءة و عملية لجدولة تطبيقات دفق الأعمال المتطلبة لقيود جودة الخدمة.
Advanced Reservation (AR) is used to guarantee resource provisioning for many different types of
applications including workflows. This technique is still under a huge controversy in both Business and
Research communities because of its potentiality of reducing resource utilization. Most of the works
proposed in this domain suggest reservation for the whole workflow schedule, and on all available
resources at the same time, which worsen the problem of resource utilization.
Many solutions are introduced to improve resource utilization under advanced reservation through
generating relaxed and elastic reservation plans that local scheduling systems could modify to improve
utilization and decrease internal fragmentation. These solutions depend mainly on changing rigid AR,
which considered to be the most difficult kind of reservation, into relaxed and elastic ones through adding
extra time on the resulted schedule and then distributing it on all tasks of the workflow.
This paper presents a new autonomic algorithm (EWARP) for producing elastic reservation plans for
workflow applications which doesn’t add extra times. Instead, it depends on exploiting the timing gaps
produced by the different scheduling algorithms. The new algorithm use the technique of discovering
timing gaps, but modifies it, and adds to it to be used for producing an elastic reservation plan for
workflows. The results presented in this paper demonstrate how the proposed algorithm outperforms
existing works in the fields by a lower bound approximating 25%.This shows that (EWARP) algorithm
offer efficient and practical solutions for the problem of scheduling workflow applications under QoS
constrains.
References used
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Many researches showed the ability of advance reservation to improve the predictability of the
system; that allows it to deliver the applications required time constrains. Applications with
many tasks require the system to ensure a number of reserv
Scheduling tasks on multiprocessors is considered one of the most
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