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From: George Neuner <gneuner2@comcast.net>
Newsgroups: comp.arch
Subject: Re: PCIe MSI-X interrupts
Date: Sun, 30 Jun 2024 00:41:05 -0400
Organization: i2pn2 (i2pn.org)
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On Fri, 28 Jun 2024 20:26:42 +0000, mitchalsup@aol.com (MitchAlsup1)
wrote:

>EricP wrote:
>
>> MitchAlsup1 wrote:
>
>>> Sounds like SNARFing
>
>> Write-update depends on broadcasting all writes if that's what snarf
>> means.
>
>General cache coherency policies broadcast a cores address to all
>caches in the system, and if that cache contains that same cache
>line, it responds with a SHARED back to requestor, or it invalidates
>the line. We call this SNOOPing. It works well.
>
>SNARF is a term whereby the owner of data broadcasts the data and
>its address, and any cache containing that line will write the
>data payload into its cache 9rather than invalidating and then
>going back and fetching it anew. For certain kinds of data struct
>SNARF is significantly more efficient than Invalidate-Refetch.
>A single message around the system performs all the needed updates,
>instead of 1 invalidate and K fetches.
>
>SNARF is almost exclusively used as side-band signals hiding under
>the cache coherent Interconnect command set.
>
>SNARF is almost never available to software. It is more like micro-
>Architecture talking to other microArchitecture.
>
>Also note: µA-to-µA is rarely of line size and often uses physical
>address bits not available through MMU tables.


Stupid question:  why is it called "snarf"?

IIRC, Snoopy (Peanuts) "scarfed" his food.  I don't recall ever seeing
Snarf (Thundercats) actually eat.