The patch titled Subject: crc32: optimize loop counter for x86 has been removed from the -mm tree. Its filename was crc32-optimize-loop-counter-for-x86.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ From: Bob Pearson <rpearson@xxxxxxxxxxxxxxxxxxxxx> Subject: crc32: optimize loop counter for x86 Add two changes that improve the performance of x86 systems 1. replace main loop with incrementing counter this change improves the performance of the selftest by about 5-6% on Nehalem CPUs. The apparent reason is that the compiler can use the loop index to perform an indexed memory access. This is reported to make the performance of PowerPC CPUs to get worse. 2. replace the rem_len loop with incrementing counter this change improves the performance of the selftest, which has more than the usual number of occurances, by about 1-2% on x86 CPUs. In actual work loads the length is most often a multiple of 4 bytes and this code does not get executed as often if at all. Again this change is reported to make the performance of PowerPC get worse. [djwong@xxxxxxxxxx: Minor changelog tweaks] Signed-off-by: Bob Pearson <rpearson@xxxxxxxxxxxxxxxxxxxxx> Signed-off-by: Darrick J. Wong <djwong@xxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- lib/crc32.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff -puN lib/crc32.c~crc32-optimize-loop-counter-for-x86 lib/crc32.c --- a/lib/crc32.c~crc32-optimize-loop-counter-for-x86 +++ a/lib/crc32.c @@ -66,6 +66,9 @@ crc32_body(u32 crc, unsigned char const # endif const u32 *b; size_t rem_len; +# ifdef CONFIG_X86 + size_t i; +# endif const u32 *t0=tab[0], *t1=tab[1], *t2=tab[2], *t3=tab[3]; const u32 *t4 = tab[4], *t5 = tab[5], *t6 = tab[6], *t7 = tab[7]; u32 q; @@ -86,7 +89,12 @@ crc32_body(u32 crc, unsigned char const # endif b = (const u32 *)buf; +# ifdef CONFIG_X86 + --b; + for (i = 0; i < len; i++) { +# else for (--b; len; --len) { +# endif q = crc ^ *++b; /* use pre increment for speed */ # if CRC_LE_BITS == 32 crc = DO_CRC4; @@ -100,9 +108,14 @@ crc32_body(u32 crc, unsigned char const /* And the last few bytes */ if (len) { u8 *p = (u8 *)(b + 1) - 1; +# ifdef CONFIG_X86 + for (i = 0; i < len; i++) + DO_CRC(*++p); /* use pre increment for speed */ +# else do { DO_CRC(*++p); /* use pre increment for speed */ } while (--len); +# endif } return crc; #undef DO_CRC _ Patches currently in -mm which might be from rpearson@xxxxxxxxxxxxxxxxxxxxx are origin.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html