Messages in this thread | | | Date | Fri, 25 May 2007 01:39:45 +0530 | From | "Satyam Sharma" <> | Subject | Re: [RFC] LZO de/compression support - take 3 |
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On 5/24/07, Nitin Gupta <nitingupta910@gmail.com> wrote: > [...] > > > > diff --git a/lib/lzo1x/lzo1x_int.h b/lib/lzo1x/lzo1x_int.h > > > > [...] > > > > +/* Macros for 'safe' decompression */ > > > > +#ifdef LZO1X_DECOMPRESS_SAFE > > > > + > > > > +#define lzo1x_decompress lzo1x_decompress_safe > > > > +#define TEST_IP (ip < ip_end) > > > > +#define NEED_IP(x) \ > > > > + if ((size_t)(ip_end - ip) < (size_t)(x)) goto input_overrun > > > > +#define NEED_OP(x) \ > > > > + if ((size_t)(op_end - op) < (size_t)(x)) goto output_overrun > > > > +#define TEST_LB(m_pos) \ > > > > + if (m_pos < out || m_pos >= op) goto lookbehind_overrun > > > > +#define HAVE_TEST_IP > > > > +#define HAVE_ANY_OP > > > > + > > > > +#else /* !LZO1X_DECOMPRESS_SAFE */ > > > > + > > > > +#define TEST_IP 1 > > > > +#define TEST_LB(x) ((void) 0) > > > > +#define NEED_IP(x) ((void) 0) > > > > +#define NEED_OP(x) ((void) 0) > > > > +#undef HAVE_TEST_IP > > > > +#undef HAVE_ANY_OP > > > > + > > > > +#endif /* LZO1X_DECOMPRESS_SAFE */ > > > > > > ... ugh. Yes, extracting the common stuff between the _safe and _unsafe > > > variants in a common low-level __lzo1x_decompress kind of function > > > definitely looks doable. The low-level function could simply take an extra > > > argument (say, set by the _safe and _unsafe wrappers) that tells it > > > whether it is being called as safe or unsafe ... helps us get rid of the > > > disruptions to all the Makefiles above and these #ifdef's ugliness ... > > > > I suspect it will probably damage performance unless the compiler is > > very clever and I don't trust compilers that much... > > +1. I looked into Satyam suggestion as above but ...yes, we should not > leave everything to compiler. And since all this was suggested just > to do away with that symlink, I don't think this splitting work is > worth the effort.
Not just the symlink ... we get rid of the changes in the two Makefiles, the -D...SAFE stuff, some #ifdef's _and_ the macros listed above. Code becomes even smaller and simpler. But yes, as I said, there'd be an extra condition tested by the _unsafe variant (and *only* the _unsafe variant, I must add) at the locations of these macros that was compiled away previously. As for performance hit, I'd be interested in actually measuring it first ... I definitely wouldn't mind trading off a couple of % for a simpler and smaller patch.
But if you don't want even _that_ performance hit, you could also simply duplicate the decompress() like Richard has done.
> For rigous testing, I have sent 'compress-test' module (with usage) to > Bret Towe who has 64-bit machines available for testing.
This test module isn't so performance benchmarking friendly, good enough for checking correctness of the algorithm implementation and robustness of the code. But I think Richard's cryptoapi glue code patch would work for your version too, as both your interfaces are the same, so that'd be a better way to benchmark the relative performance of your patch vs his. If you can test/benchmark both your versions and produce results that beat his code, you've made it :-) - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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