Changes in mmx.c

dd165a65 - treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 48

Mon, 20 May 2019 17:08:13 +0000

treewide: Replace GPLv2 boilerplate/reference with SPDX - rule 48Based on 1 normalized pattern(s): this program is free software you can redistribute it and or modify it under the terms of the gnu general public license as published by the free software foundation inc 53 temple place ste 330 boston ma 02111 1307 usa either version 2 of the license or at your option any later version incorporated herein by referenceextracted by the scancode license scanner the SPDX license identifier GPL-2.0-or-laterhas been chosen to replace the boilerplate/reference in 13 file(s).Signed-off-by: Thomas Gleixner Reviewed-by: Allison Randal Reviewed-by: Kate Stewart Cc: linux-spdx@vger.kernel.orgLink: https://lkml.kernel.org/r/20190520170858.645641371@linutronix.deSigned-off-by: Greg Kroah-Hartman List of files: /linux-6.15/lib/raid6/mmx.c

fe5cbc6e - md/raid6 algorithms: delta syndrome functions

Mon, 15 Dec 2014 01:57:04 +0000

md/raid6 algorithms: delta syndrome functionsv3: s-o-b comment, explanation of performance and descision forthe start/stop implementationImplementing rmw functionality for RAID6 requires optimized syndromecalculation. Up to now we can only generate a complete syndrome. Thetarget P/Q pages are always overwritten. With this patch we providea framework for inplace P/Q modification. In the first place simplyfill those functions with NULL values.xor_syndrome() has two additional parameters: start & stop. Thesewill indicate the first and last page that are changing during armw run. That makes it possible to avoid several unneccessary loopsand speed up calculation. The caller needs to implement the followinglogic to make the functions work.1) xor_syndrome(disks, start, stop, ...): "Remove" all data of sourceblocks inside P/Q between (and including) start and end.2) modify any block with start <= block <= stop3) xor_syndrome(disks, start, stop, ...): "Reinsert" all data ofsource blocks into P/Q between (and including) start and end.Pages between start and stop that won't be changed should be filledwith a pointer to the kernel zero page. The reasons for not taking NULLpages are:1) Algorithms cross the whole source data line by line. Thus avoidadditional branches.2) Having a NULL page avoids calculating the XOR P parity but stillneed calulation steps for the Q parity. Depending on the algorithmunrolling that might be only a difference of 2 instructions per loop.The benchmark numbers of the gen_syndrome() functions are displayed inthe kernel log. Do the same for the xor_syndrome() functions. Thiswill help to analyze performance problems and give an rough estimatehow well the algorithm works. The choice of the fastest algorithm willstill depend on the gen_syndrome() performance.With the start/stop page implementation the speed can vary a lot in reallife. E.g. a change of page 0 & page 15 on a stripe will be harder tocompute than the case where page 0 & page 1 are XOR candidates. To be notto enthusiatic about the expected speeds we will run a worse case testthat simulates a change on the upper half of the stripe. So we do:1) calculation of P/Q for the upper pages2) continuation of Q for the lower (empty) pagesSigned-off-by: Markus Stockhausen Signed-off-by: NeilBrown List of files: /linux-6.15/lib/raid6/mmx.c

4f8c55c5 - lib/raid6: build proper files on corresponding arch

Fri, 30 Nov 2012 21:10:40 +0000

lib/raid6: build proper files on corresponding archsse and avx2 stuff only exist on x86 arch, and we don't need to buildaltivec on x86. And we can do that at lib/raid6/Makefile.Proposed-by: H. Peter Anvin Signed-off-by: Yuanhan Liu Reviewed-by: H. Peter Anvin Signed-off-by: Jim Kukunas Signed-off-by: NeilBrown List of files: /linux-6.15/lib/raid6/mmx.c

a8e026c7 - Further tidyup of raid6 naming in lib/raid6

Wed, 11 Aug 2010 20:44:54 +0000

Further tidyup of raid6 naming in lib/raid6Rename raid6/raid6x86.h to raid6/x86.hand modify some comments.Signed-off-by: NeilBrown List of files: /linux-6.15/lib/raid6/mmx.c

cc4589eb - Rename raid6 files now they're in a 'raid6' directory.

Tue, 10 Aug 2010 23:19:05 +0000

Rename raid6 files now they're in a 'raid6' directory.Linus asks 'why "raid6" twice?'. No reason.Signed-off-by: David Woodhouse List of files: /linux-6.15/lib/raid6/mmx.c