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This is to avoid name clashes for the introduction of a global swap()
macro.
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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Hello, I fixed and tested a small bug in lib/sort.c file, heap sort
function.
The fix avoids unnecessary swap of contents when i is 0 (saves few loads
and stores), which happens every time sort function is called. I felt the
fix is worth bringing it to your attention given the importance and
frequent use of the sort function.
Acked-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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A variety of (mostly) innocuous fixes to the embedded kernel-doc content in
source files, including:
* make multi-line initial descriptions single line
* denote some function names, constants and structs as such
* change erroneous opening '/*' to '/**' in a few places
* reword some text for clarity
Signed-off-by: Robert P. J. Day <rpjday@mindspring.com>
Cc: "Randy.Dunlap" <rdunlap@xenotime.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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It is a non-standard heap-sort algorithm implementation because the index
of child node is wrong . The sort function still outputs right result, but
the performance is O( n * ( log(n) + 1 ) ) , about 10% ~ 20% worse than
standard algorithm.
Signed-off-by: keios <keios.cn@gmail.com>
Acked-by: Matt Mackall <mpm@selenic.com>
Acked-by: Zou Nan hai <nanhai.zou@intel.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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I recently picked up my older work to remove unnecessary #includes of
sched.h, starting from a patch by Dave Jones to not include sched.h
from module.h. This reduces the number of indirect includes of sched.h
by ~300. Another ~400 pointless direct includes can be removed after
this disentangling (patch to follow later).
However, quite a few indirect includes need to be fixed up for this.
In order to feed the patches through -mm with as little disturbance as
possible, I've split out the fixes I accumulated up to now (complete for
i386 and x86_64, more archs to follow later) and post them before the real
patch. This way this large part of the patch is kept simple with only
adding #includes, and all hunks are independent of each other. So if any
hunk rejects or gets in the way of other patches, just drop it. My scripts
will pick it up again in the next round.
Signed-off-by: Tim Schmielau <tim@physik3.uni-rostock.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch contains the following small cleanups:
- make two needlessly global functions static
- every file should #include the header files containing the prototypes
of it's global functions
Signed-off-by: Adrian Bunk <bunk@stusta.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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The regression test in lib/sort.c is currently worthless because the array
that is generated for sorting will be all zeros. This patch fixes things
so that the array that is generated will contain unsorted integers (that
are not all identical) as was probably intended.
Signed-off-by Daniel Dickman <didickman@yahoo.com>
Signed-off-by: Domen Puncer <domen@coderock.org>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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This patch adds a generic array sorting library routine. This is meant
to replace qsort, which has two problem areas for kernel use.
The first issue is quadratic worst-case performance. While quicksort
worst-case datasets are rarely encountered in normal scenarios, it is
in fact quite easy to construct worst cases for almost all quicksort
algorithms given source or access to an element comparison callback.
This could allow attackers to cause sorts that would otherwise take
less than a millisecond to take seconds and sorts that should take
less than a second to take weeks or months. Fixing this problem
requires randomizing pivot selection with a secure random number
generator, which is rather expensive.
The second is that quicksort's recursion tracking requires either
nontrivial amounts of stack space or dynamic memory allocation and out
of memory error handling.
By comparison, heapsort has both O(n log n) average and worst-case
performance and practically no extra storage requirements. This
version runs within 70-90% of the average performance of optimized
quicksort so it should be an acceptable replacement wherever quicksort
would be used in the kernel.
Note that this function has an extra parameter for passing in an
optimized swapping function. This is worth 10% or more over the
typical byte-by-byte exchange functions.
Benchmarks:
qsort: glibc variant 1189 bytes (+ 256/1024 stack)
qsort_3f: my simplified variant 459 bytes (+ 256/1024 stack)
heapsort: the version below 346 bytes
shellsort: an optimized shellsort 196 bytes
P4 1.8GHz Opteron 1.4GHz (32-bit)
size algorithm cycles relative cycles relative
100:
qsort: 38682 100.00% 27631 100.00%
qsort_3f: 36277 106.63% 22406 123.32%
heapsort: 43574 88.77% 30301 91.19%
shellsort: 39087 98.97% 25139 109.91%
200:
qsort: 86468 100.00% 61148 100.00%
qsort_3f: 78918 109.57% 48959 124.90%
heapsort: 98040 88.20% 68235 89.61%
shellsort: 95688 90.36% 62279 98.18%
400:
qsort: 187720 100.00% 131313 100.00%
qsort_3f: 174905 107.33% 107954 121.64%
heapsort: 223896 83.84% 154241 85.13%
shellsort: 223037 84.17% 148990 88.14%
800:
qsort: 407060 100.00% 287460 100.00%
qsort_3f: 385106 105.70% 239131 120.21%
heapsort: 484662 83.99% 340099 84.52%
shellsort: 537110 75.79% 354755 81.03%
1600:
qsort: 879596 100.00% 621331 100.00%
qsort_3f: 861568 102.09% 522013 119.03%
heapsort: 1079750 81.46% 746677 83.21%
shellsort: 1234243 71.27% 820782 75.70%
3200:
qsort: 1903902 100.00% 1342126 100.00%
qsort_3f: 1908816 99.74% 1131496 118.62%
heapsort: 2515493 75.69% 1630333 82.32%
shellsort: 2985339 63.78% 1964794 68.31%
6400:
qsort: 4046370 100.00% 2909215 100.00%
qsort_3f: 4164468 97.16% 2468393 117.86%
heapsort: 5150659 78.56% 3533585 82.33%
shellsort: 6650225 60.85% 4429849 65.67%
12800:
qsort: 8729730 100.00% 6185097 100.00%
qsort_3f: 8776885 99.46% 5288826 116.95%
heapsort: 11064224 78.90% 7603061 81.35%
shellsort: 15487905 56.36% 10305163 60.02%
25600:
qsort: 18357770 100.00% 13172205 100.00%
qsort_3f: 18687842 98.23% 11337115 116.19%
heapsort: 24121241 76.11% 16612122 79.29%
shellsort: 35552814 51.64% 24106987 54.64%
51200:
qsort: 38658883 100.00% 28008505 100.00%
qsort_3f: 39498463 97.87% 24339675 115.07%
heapsort: 50553552 76.47% 37013828 75.67%
shellsort: 82602416 46.80% 56201889 49.84%
102400:
qsort: 81197794 100.00% 58918933 100.00%
qsort_3f: 84257930 96.37% 51986219 113.34%
heapsort: 110540577 73.46% 81419675 72.36%
shellsort: 191303132 42.44% 129786472 45.40%
From: Zou Nan hai <nanhai.zou@intel.com>
The new sort routine only works if there are an even number of entries in
the ia64 exception fix-up tables. If the number of entries is odd the sort
fails, and then random get_user/put_user calls can fail.
Signed-off-by: Matt Mackall <mpm@selenic.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
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