*Rani of Hearts-Reena Kapoor Paristan#55*The Cave Woman - Page 7

so multiprocessing is aka multicore .. hmm didnt know that from attending lec.. probably slept 🤪

ok i wanna write down stuff which is not in slides but might appear... MIGHT

SMP - symmetric multiprocessing architecture

multiple processors connected to memory with single bus

all processors treated equally

no processor reserved for specific purpose

advantages:

has cost effective ways to increase throughput

disadvantages:

limits on scalability due to cache coherence and shared objects

• lacks cache affinity (i dont know why.. yaad ni aarha mam ne kya btaya tha )
• does not scale well
• sync problem

multilevel queue  ^

adv: 

no sync overhead

provides cache affinity

disadv:

load imbalancing

for load imabalanced issue

we can migrate processes to other queues

-when is it ok to migrate?

-scalability problems?

-how often to migrate?

group scheduling

so basically related threads different CPUs pe hote he lakin ek hi time pe start aur end hote he taake sync kr ske 👍🏼😃

itni si baat thi.. lol

challenges of modern computer hardware

NUMA - non uniform memory access latencies

synchronization costs

gap between cpu and memory latencies

cache coherence cost

load balancer should work on:

not number of threads

not weight

but on

load = weight + average CPU utilization

-cgroup -> load further divided by total number of threads of cgroup

cache locality:

temporal locality:

a piece of data can be accessed again in near future

spatial locality:

if data is accessed at address x then data near that address can also be accessed in near future