After I installed a newer version of Kernel (2.4.2) and enable DMA option in
hardware configuration, the behavior changes.
I can see performance improvements when another thread is used. Also, i can
see timing overlaps between two threads. i.e. when one thread is blocked on a
page fault, other thread keeps working.
Now, how can this behavior be explained , given the earlier argument.
Is it that, a newer version of kernel has fixed the problem of the semaphore
?
thanks
neelam
> That's a known problem:
>
> The paging io for a process is controlled with a per-process semaphore.
> The semaphore is held while waiting for the actual io. Thus the paging
> in multi threaded applications is single threaded.
> Probably your prefetch thread is waiting for disk io, and the worker
> thread causes a minor pagefault --> worker thread sleeps until the disk
> io is completed.
>
> --
> Manfred
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