radix-tree: introduce bit-optimized iterator
A series of radix tree cleanups, and usage of them in the core pagecache
code.
Micro-benchmark:
lookup 14 slots (typical page-vector size)
in radix-tree there earch <step> slot filled and tagged
before/after - nsec per full scan through tree
* Intel Sandy Bridge i7-2620M 4Mb L3
New code always faster
* AMD Athlon 6000+ 2x1Mb L2, without L3
New code generally faster,
Minor degradation (marked with "*") for huge sparse trees
* i386 on Sandy Bridge
New code faster for common cases: tagged and dense trees.
Some degradations for non-tagged lookup on sparse trees.
Ideally, there might help __ffs() analog for searching first non-zero
long element in array, gcc sometimes cannot optimize this loop corretly.
Numbers:
CPU: Intel Sandy Bridge i7-2620M 4Mb L3
radix-tree with 1024 slots:
tagged lookup
step 1 before 7156 after 3613
step 2 before 5399 after 2696
step 3 before 4779 after 1928
step 4 before 4456 after 1429
step 5 before 4292 after 1213
step 6 before 4183 after 1052
step 7 before 4157 after 951
step 8 before 4016 after 812
step 9 before 3952 after 851
step 10 before 3937 after 732
step 11 before 4023 after 709
step 12 before 3872 after 657
step 13 before 3892 after 633
step 14 before 3720 after 591
step 15 before 3879 after 578
step 16 before 3561 after 513
normal lookup
step 1 before 4266 after 3301
step 2 before 2695 after 2129
step 3 before 2083 after 1712
step 4 before 1801 after 1534
step 5 before 1628 after 1313
step 6 before 1551 after 1263
step 7 before 1475 after 1185
step 8 before 1432 after 1167
step 9 before 1373 after 1092
step 10 before 1339 after 1134
step 11 before 1292 after 1056
step 12 before 1319 after 1030
step 13 before 1276 after 1004
step 14 before 1256 after 987
step 15 before 1228 after 992
step 16 before 1247 after 999
radix-tree with 1024*1024*128 slots:
tagged lookup
step 1 before
1086102841 after
674196409
step 2 before
816839155 after
498138306
step 7 before
599728907 after
240676762
step 15 before
555729253 after
185219677
step 63 before
606637748 after
128585664
step 64 before
608384432 after
102945089
step 65 before
596987114 after
123996019
step 128 before
304459225 after
56783056
step 256 before
158846855 after
31232481
step 512 before
86085652 after
18950595
step 12345 before
6517189 after
1674057
normal lookup
step 1 before
626064869 after
544418266
step 2 before
418809975 after
336321473
step 7 before
242303598 after
207755560
step 15 before
208380563 after
176496355
step 63 before
186854206 after
167283638
step 64 before
176188060 after
170143976
step 65 before
185139608 after
167487116
step 128 before
88181865 after
86913490
step 256 before
45733628 after
45143534
step 512 before
24506038 after
23859036
step 12345 before
2177425 after
2018662
* AMD Athlon 6000+ 2x1Mb L2, without L3
radix-tree with 1024 slots:
tag-lookup
step 1 before 8164 after 5379
step 2 before 5818 after 5581
step 3 before 4959 after 4213
step 4 before 4371 after 3386
step 5 before 4204 after 2997
step 6 before 4950 after 2744
step 7 before 4598 after 2480
step 8 before 4251 after 2288
step 9 before 4262 after 2243
step 10 before 4175 after 2131
step 11 before 3999 after 2024
step 12 before 3979 after 1994
step 13 before 3842 after 1929
step 14 before 3750 after 1810
step 15 before 3735 after 1810
step 16 before 3532 after 1660
normal-lookup
step 1 before 7875 after 5847
step 2 before 4808 after 4071
step 3 before 4073 after 3462
step 4 before 3677 after 3074
step 5 before 4308 after 2978
step 6 before 3911 after 3807
step 7 before 3635 after 3522
step 8 before 3313 after 3202
step 9 before 3280 after 3257
step 10 before 3166 after 3083
step 11 before 3066 after 3026
step 12 before 2985 after 2982
step 13 before 2925 after 2924
step 14 before 2834 after 2808
step 15 before 2805 after 2803
step 16 before 2647 after 2622
radix-tree with 1024*1024*128 slots:
tag-lookup
step 1 before
1288059720 after
951736580
step 2 before
961292300 after
884212140
step 7 before
768905140 after
547267580
step 15 before
771319480 after
456550640
step 63 before
504847640 after
242704304
step 64 before
392484800 after
177920786
step 65 before
491162160 after
246895264
step 128 before
208084064 after
97348392
step 256 before
112401035 after
51408126
step 512 before
75825834 after
29145070
step 12345 before
5603166 after
2847330
normal-lookup
step 1 before
1025677120 after
861375100
step 2 before
647220080 after
572258540
step 7 before
505518960 after
484041813
step 15 before
430483053 after
444815320 *
step 63 before
388113453 after
404250546 *
step 64 before
374154666 after
396027440 *
step 65 before
381423973 after
396704853 *
step 128 before
190078700 after
202619384 *
step 256 before
100886756 after
102829108 *
step 512 before
64074505 after
56158720
step 12345 before
4237289 after
4422299 *
* i686 on Sandy bridge
radix-tree with 1024 slots:
tagged lookup
step 1 before 7990 after 4019
step 2 before 5698 after 2897
step 3 before 5013 after 2475
step 4 before 4630 after 1721
step 5 before 4346 after 1759
step 6 before 4299 after 1556
step 7 before 4098 after 1513
step 8 before 4115 after 1222
step 9 before 3983 after 1390
step 10 before 4077 after 1207
step 11 before 3921 after 1231
step 12 before 3894 after 1116
step 13 before 3840 after 1147
step 14 before 3799 after 1090
step 15 before 3797 after 1059
step 16 before 3783 after 745
normal lookup
step 1 before 5103 after 3499
step 2 before 3299 after 2550
step 3 before 2489 after 2370
step 4 before 2034 after 2302 *
step 5 before 1846 after 2268 *
step 6 before 1752 after 2249 *
step 7 before 1679 after 2164 *
step 8 before 1627 after 2153 *
step 9 before 1542 after 2095 *
step 10 before 1479 after 2109 *
step 11 before 1469 after 2009 *
step 12 before 1445 after 2039 *
step 13 before 1411 after 2013 *
step 14 before 1374 after 2046 *
step 15 before 1340 after 1975 *
step 16 before 1331 after 2000 *
radix-tree with 1024*1024*128 slots:
tagged lookup
step 1 before
1225865377 after
667153553
step 2 before
842427423 after
471533007
step 7 before
609296153 after
276260116
step 15 before
544232060 after
226859105
step 63 before
519209199 after
141343043
step 64 before
588980279 after
141951339
step 65 before
521099710 after
138282060
step 128 before
298476778 after
83390628
step 256 before
149358342 after
43602609
step 512 before
76994713 after
22911077
step 12345 before
5328666 after
1472111
normal lookup
step 1 before
819284564 after
533635310
step 2 before
512421605 after
364956155
step 7 before
271443305 after
305721345 *
step 15 before
223591630 after
273960216 *
step 63 before
190320247 after
217770207 *
step 64 before
178538168 after
267411372 *
step 65 before
186400423 after
215347937 *
step 128 before
88106045 after
140540612 *
step 256 before
44812420 after
70660377 *
step 512 before
24435438 after
36328275 *
step 12345 before
2123924 after
2148062 *
bloat-o-meter delta for this patchset + patchset with related shmem cleanups
bloat-o-meter: x86_64
add/remove: 4/3 grow/shrink: 5/6 up/down: 928/-939 (-11)
function old new delta
radix_tree_next_chunk - 499 +499
shmem_unuse 428 554 +126
shmem_radix_tree_replace 131 227 +96
find_get_pages_tag 354 419 +65
find_get_pages_contig 345 407 +62
find_get_pages 362 396 +34
__kstrtab_radix_tree_next_chunk - 22 +22
__ksymtab_radix_tree_next_chunk - 16 +16
__kcrctab_radix_tree_next_chunk - 8 +8
radix_tree_gang_lookup_slot 204 203 -1
static.shmem_xattr_set 384 381 -3
radix_tree_gang_lookup_tag_slot 208 191 -17
radix_tree_gang_lookup 231 187 -44
radix_tree_gang_lookup_tag 247 199 -48
shmem_unlock_mapping 278 190 -88
__lookup 217 - -217
__lookup_tag 242 - -242
radix_tree_locate_item 279 - -279
bloat-o-meter: i386
add/remove: 3/3 grow/shrink: 8/9 up/down: 1075/-1275 (-200)
function old new delta
radix_tree_next_chunk - 757 +757
shmem_unuse 352 449 +97
find_get_pages_contig 269 322 +53
shmem_radix_tree_replace 113 154 +41
find_get_pages_tag 277 318 +41
dcache_dir_lseek 426 458 +32
__kstrtab_radix_tree_next_chunk - 22 +22
vc_do_resize 968 977 +9
snd_pcm_lib_read1 725 733 +8
__ksymtab_radix_tree_next_chunk - 8 +8
netlbl_cipsov4_list 1120 1127 +7
find_get_pages 293 291 -2
new_slab 467 459 -8
bitfill_unaligned_rev 425 417 -8
radix_tree_gang_lookup_tag_slot 177 146 -31
blk_dump_cmd 267 229 -38
radix_tree_gang_lookup_slot 212 134 -78
shmem_unlock_mapping 221 128 -93
radix_tree_gang_lookup_tag 275 162 -113
radix_tree_gang_lookup 255 126 -129
__lookup 227 - -227
__lookup_tag 271 - -271
radix_tree_locate_item 277 - -277
This patch:
Implement a clean, simple and effective radix-tree iteration routine.
Iterating divided into two phases:
* lookup next chunk in radix-tree leaf node
* iterating through slots in this chunk
Main iterator function radix_tree_next_chunk() returns pointer to first
slot, and stores in the struct radix_tree_iter index of next-to-last slot.
For tagged-iterating it also constuct bitmask of tags for retunted chunk.
All additional logic implemented as static-inline functions and macroses.
Also adds radix_tree_find_next_bit() static-inline variant of
find_next_bit() optimized for small constant size arrays, because
find_next_bit() too heavy for searching in an array with one/two long
elements.
[akpm@linux-foundation.org: rework comments a bit]
Signed-off-by: Konstantin Khlebnikov <khlebnikov@openvz.org>
Tested-by: Hugh Dickins <hughd@google.com>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
projects / openwrt / staging / blogic.git / commit