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Most of these calls have since been serialized?

Most of these calls have since been serialized?

Posted Nov 17, 2005 15:33 UTC (Thu) by snitm (guest, #4031)
Parent article: 4K stacks - again

Could someone elaborate on what it means to 'serialize' the historically long call chains associated with block devices + lvm2 + nfs + firewall, etc?


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Most of these calls have since been serialized?

Posted Nov 17, 2005 15:46 UTC (Thu) by fenrus (guest, #31654) [Link]

it goes like this; there is a key function that is used to submit IO
and DM and co need to change the IO a bit and then cause it to be submitted again

XFS -> function -> dm layer -> function -> dm layer -> function -> raid layer -> function -> scsi layer -> driver

(well theoretical example but you get the idea I hope)

in the new situation, instead of calling the function again, you return "do again" so it goes like

XFS -> function -> dm layer -|
function -> dm layer -|
function -> raid layer -|
function -> scsi layer -> driver

so the max depth is 4 (well real world is slightly more complex) independent on how often you layer this. In the old situation you could layer a lot and go really big (11 in the example, but just layer more and it goes higher)


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