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

From: David Miller
Date: Mon Jul 14 2008 - 08:29:16 EST


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.

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