[nvmewin] nvmewin Digest, Vol 4, Issue 27

[Luse, Paul E]

Actually I've got another more academic approach that I'm testing now and have written unit test code to cover all test cases that runs just against this little section that determines the number of PPR entries.  Once I have it, and the test code, ready I'll send them out.  We should actually have a contest for the simplest/tightest algorithm to solve this fairly simple problem... my current routine only has 2 conditions and 5 operations as compared to the 4 conditions and 11 operations that we currently use

-----Original Message-----
From: Luse, Paul E 
Sent: Wednesday, April 18, 2012 6:26 PM
To: Harris, James R; nvmewin at lists.openfabrics.org
Subject: RE: nvmewin Digest, Vol 4, Issue 27

Actually it doesn't, I don't think.  If you're less than a page size and have an offset and just go down the else side you'll end up with a bogus start/end address and the math to calculate the num of whole pages will be negative.  I could have generically determined if the element crossed a page boundary and if not just set the num entries to 1 and if so drop to the else and that would work too.  It wouldn't save any cycles though but would pull the part out about calc'ing the next starting page into common code.  I didn't think it was worth it.

Thoughts?

-----Original Message-----
From: nvmewin-bounces at lists.openfabrics.org [mailto:nvmewin-bounces at lists.openfabrics.org] On Behalf Of Harris, James R
Sent: Wednesday, April 18, 2012 5:47 PM
To: nvmewin at lists.openfabrics.org
Subject: Re: [nvmewin] nvmewin Digest, Vol 4, Issue 27

You shouldn't need the "if" part here.  The "else" part will handle the "less than PAGE_SIZE" case.

-Jim


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>Subject: nvmewin Digest, Vol 4, Issue 27
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>Today's Topics:
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>   1. updated SGL conversion routine (Luse, Paul E)
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>----------------------------------------------------------------------
>
>Message: 1
>Date: Thu, 19 Apr 2012 00:43:02 +0000
>From: "Luse, Paul E" <paul.e.luse at intel.com>
>To: "nvmewin at lists.openfabrics.org" <nvmewin at lists.openfabrics.org>
>Subject: [nvmewin] updated SGL conversion routine
>Message-ID:
>	<82C9F782B054C94B9FC04A331649C77A0BAFC5 at FMSMSX106.amr.corp.intel.com>
>Content-Type: text/plain; charset="us-ascii"
>
>OK, the else has now been updated (thanks Jim, needed some tweaks 
>though but I saw what you were going for of course).  There's so many 
>way to handle this problem, I'm sure we can find something more efficient than this but its pretty good I think and easy to follow.
>
>Please review, I have this under test now and am heading out....
>
>Thx
>Paul
>
>
>        physicalAddress.QuadPart =
> pSgl->List[index].PhysicalAddress.QuadPart;
>
>        if (sgElementSize <= PAGE_SIZE) {
>            ULONG nextPage = 0;
>
>            /* Must transfer at least one full page */
>            numImplicitEntries = 1;
>            /*
>             * since we may be offset into the page, look to determine
>             * address to determine if a 2nd PRP entry is needed
>             */
>            nextPage = physicalAddress.LowPart + PAGE_SIZE;
>            nextPage = nextPage & ~PAGE_MASK;
>            numImplicitEntries +=
>                ((physicalAddress.LowPart + sgElementSize) > nextPage) ? 1 : 0;
>        } else {
>            PHYSICAL_ADDRESS startAddr, endAddr;
>
>            startAddr.QuadPart = physicalAddress.QuadPart;
>            endAddr.QuadPart = startAddr.QuadPart + sgElementSize;
>            numImplicitEntries = 0;
>
>            /* account for an entry becaue of an offset start */
>            if (startAddr.QuadPart % PAGE_SIZE) {
>                numImplicitEntries += 1;
>                /* bump the start address to the next page boundary */
>                startAddr.QuadPart += PAGE_SIZE;
>                startAddr.QuadPart &= ~PAGE_MASK;
>            }
>
>            /* account for an entry becaue of tail */
>            if (endAddr.QuadPart % PAGE_SIZE) {
>                numImplicitEntries += 1;
>                /* lop off the tail */
>                endAddr.QuadPart &= ~PAGE_MASK;
>            }
>            /* now account for the whole pages if any */
>            numImplicitEntries += (ULONG)((endAddr.QuadPart - startAddr.QuadPart) / PAGE_SIZE);
>        }
>
>____________________________________
>Paul Luse
>Sr. Staff Engineer
>PCG Server Software Engineering
>Desk: 480.554.3688, Mobile: 480.334.4630
>
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