Re: [PATCH 34/35] async: use workqueue for worker pool
From: Arjan van de Ven
Date: Tue Jun 29 2010 - 14:07:26 EST
On 6/29/2010 9:59 AM, Tejun Heo wrote:
On 06/29/2010 06:40 PM, Arjan van de Ven wrote:
uh? clearly the assumption is that if I have a 16 CPU machine, and 12Hmmm... workqueue workers are bound to certain cpu, so if you schedule
items of work get scheduled,
that we get all 12 running in parallel. All the smarts of cmwq surely
only kick in once you've reached the
"one work item per cpu" threshold ???
a work on a specific CPU, it will run there. Once a cpu gets
saturated, the issuing thread will be moved elsewhere. I don't think
it matters to any of the current async users one way or the other,
we might be talking past eachother. ;-)
let me define an example that is simple so that we can get on the same page
assume a system with "enough" cpus, say 32.
lets say we have 2 async tasks, that each do an mdelay(1000); (yes I
know stupid, but exagerating things makes things easier to talk about)
lets also assume that they get scheduled right back to back from the
same code on the same cpu.
will the end result be that the first mdelay() task complete before the
second one gets started, or will the end result be that
the 2nd one will notice the first cpu is busy, and find a second cpu to
run in parallel with.
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