Re: [SUGGESTION]: drop virtual merge accounting in I/O requests

[Mikulas Patocka]

On Mon, 14 Jul 2008, David Miller wrote:

> From: Mikulas Patocka <mpatocka@xxxxxxxxxx>
> Date: Mon, 14 Jul 2008 08:16:13 -0400 (EDT)
>
> > As you mentioned ESP driver, it declares .sg_tablesize = SG_ALL, so
> > BIO_VMERGE_BOUNDARY has no effect on the operation of this driver. Any
> > other driver where BIO_VMERGE_BOUNDARY does matter?
>
> When BIO_VMERGE_BOUNDARY is turned on, requests that would not
> otherwise fit into the device's limits, can.

Why would someone want to overshoot SG_ALL? ... and, shouldn't the 
constant be increased then --- instead of making buggy BIO_VMERGE_BOUNDARY 
expectations?

Mikulas

> It's the only way to know ahead of time that the IOMMU is going
> to merge things for us.

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