Messages in this thread | | | Date | Fri, 30 Sep 2011 09:12:23 -0700 | From | "Darrick J. Wong" <> | Subject | Re: [PATCH v3] crc32c: Implement CRC32c with slicing-by-8 algorithm |
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[putting mailing lists on cc]
On Fri, Sep 30, 2011 at 08:01:36AM +0200, Joakim Tjernlund wrote: > > (Just happen to see this patch in the archives) > > - This is basically an copy of Bobs crc32 work and duplicates code, this > code needs to move into /lib/crc32.c and use the existing framework.
Which framework are you talking about? lib/crc32.c appears to be a simple module that exports a utility function. Do you mean that you want to merge the crc32{,c}defs.h and gen_crc32{,c}table.c code? Do you want a build script that starts with only a crc${ALG}_defs.h file and stamps out gencrc${ALG}_table.c and crc${ALG}.c boilerplate code and then builds it?
I really don't know; from my perspective there was a slow implementation in crypto/crc32c.c and I wanted to speed it up. crc32c seems to be in crypto/ and not lib/ so that the implementation can be replaced with a hardware accelerated version at runtime (crc32c-intel).
For crc32 which has no such hw replacement (as far as I know), moving it into crypto/ would incur the overhead of going through the cryptoapi for not much benefit. On the other hand it wouldn't be hard to put the crc32 code into crypto/. > > - Slice by 8 is just half the speed on my ppc32 compared to slice by 4 so > it can't be enabled for all archs. Best to start with all 64 bit archs
<shrug> I suppose I could make CRC32C_BITS configurable. What is the hardware profile of your ppc32 processor? How much L1D/L2 cache? slice-by-8 does have a big cache footprint. On the other hand it's faster than the slice-by-4 (crc32) and Sarwate (crc32c) code in the kernel, even on old slow 32-bit x86 processors (PII, PIII, P4).
> - Last time I tested Bobs slice by 8 on ppc32 it didn't work.
... is crc32c broken *now*? It seems fine on x86/amd64/ppc64.
--D
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