Re: [RESEND][RFC] BFQ I/O Scheduler

[Avi Kivity <avi@qumranet.com>]

Paolo Valente wrote:
> Avi Kivity ha scritto:
>> Jumping in at random, does "process" here mean task or mms_struct?  
>> If the former, doesn't that mean that a 100-thread process can starve 
>> out a single-threaded process?
>>
>> Perhaps we need hierarchical io scheduling, like cfs has for the cpu.
>>
> Hierarchical would simplify isolating groups of threads or processes.
> However, some simple solution is already available with bfq. For 
> example, if you have to fairly share the disk bandwidth between the 
> above 100 threads and another important thread, you get it by just 
> assigning weight 1 to each of these 100 threads, and weight 100 to the 
> important one.

Doesn't work.  If the 100-thread process wants to use just on thread for 
issuing I/O, it will be starved by the single-threaded process.

[my example has process A with 100 threads, and process B with 1 thread, 
not a 101-thread process with one important thread]


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