kevin/linux
1
Fork 0
Code
25db711df3
linux/lib
History
David Howells 690d137f44 Reduce the number of expensive division instructions done by _parse_integer() 
_parse_integer() does one or two division instructions (which are slow)
per digit parsed to perform the overflow check.

Furthermore, these are particularly expensive examples of division
instruction as the number of clock cycles required to complete them may
go up with the position of the most significant set bit in the dividend:

	if (*res > div_u64(ULLONG_MAX - val, base))

which is as maximal as possible.

Worse, on 32-bit arches, more than one of these division instructions
may be required per digit.

So, assuming we don't support a base of more than 16, skip the check if the
top nibble of the result is not set at this point.

Signed-off-by: David Howells <dhowells@redhat.com>
[ Changed it to not dereference the pointer all the time - even if the
  compiler can and does optimize it away, the code just looks cleaner.
  And edited the top nybble test slightly to make the code generated on
  x86-64 better in the loop - test against a hoisted constant instead of
  shifting and testing the result ]
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-02-09 10:09:30 -08:00
..
lzo
mpi lib: Fix 32-bit sparc udiv_qrnnd() definition in mpilib's longlong.h 2012-02-02 10:34:25 +11:00
raid6 md: Add in export.h for files using EXPORT_SYMBOL 2011-10-31 19:31:19 -04:00
reed_solomon
xz XZ: Fix incorrect XZ_BUF_ERROR 2011-09-21 13:39:59 -07:00
zlib_deflate zlib: slim down zlib_deflate() workspace when possible 2011-03-22 17:44:17 -07:00
zlib_inflate
.gitignore
argv_split.c
atomic64_test.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
atomic64.c lib: atomic64: Change the type of local lock to raw_spinlock_t 2011-09-14 13:14:11 +02:00
audit.c audit: support the "standard" <asm-generic/unistd.h> 2011-05-04 14:41:28 -04:00
average.c
bcd.c
bch.c lib: add shared BCH ECC library 2011-03-11 14:25:50 +00:00
bitmap.c lib/bitmap.c: quiet sparse noise about address space 2011-10-31 17:30:56 -07:00
bitrev.c
bsearch.c lib: Add generic binary search function to the kernel. 2011-05-19 16:55:27 +09:30
btree.c btree: export btree_get_prev() so modules can use btree_for_each 2012-01-10 16:30:49 -08:00
bug.c bugs, x86: Fix printk levels for panic, softlockups and stack dumps 2012-01-26 21:28:45 +01:00
bust_spinlocks.c
check_signature.c
checksum.c lib/checksum.c: optimize do_csum a bit 2011-07-07 04:52:24 -07:00
clz_tab.c lib: Fix multiple definitions of clz_tab 2012-02-02 10:34:23 +11:00
cmdline.c
cordic.c Docs: wording: functions -> algorithm 2011-10-29 21:20:22 +02:00
cpu_rmap.c lib: cpu_rmap: CPU affinity reverse-mapping 2011-01-24 14:51:56 -08:00
cpu-notifier-error-inject.c
cpumask.c cpumask: alloc_cpumask_var() use NUMA_NO_NODE 2011-07-26 16:49:44 -07:00
crc7.c
crc8.c lib: crc8: add new library module providing crc8 algorithm 2011-06-03 15:01:06 -04:00
crc16.c
crc32.c crc32: optimize inner loop 2012-01-10 16:30:51 -08:00
crc32defs.h
crc-ccitt.c
crc-itu-t.c
crc-t10dif.c
ctype.c
debug_locks.c
debugobjects.c debugobjects: Extend to assert that an object is initialized 2011-11-23 18:49:22 +01:00
dec_and_lock.c atomic: use <linux/atomic.h> 2011-07-26 16:49:47 -07:00
decompress_bunzip2.c decompress_bunzip2: remove invalid vi modeline 2011-12-06 10:00:05 +01:00
decompress_inflate.c decompressors: check input size in decompress_inflate.c 2011-01-13 08:03:25 -08:00
decompress_unlzma.c treewide: Fix comment and string typo 'bufer' 2011-12-06 09:53:40 +01:00
decompress_unlzo.c unlzo: fix input buffer free 2012-01-12 20:13:13 -08:00
decompress_unxz.c Fix common misspellings 2011-03-31 11:26:23 -03:00
decompress.c decompressors: add boot-time XZ support 2011-01-13 08:03:25 -08:00
devres.c Merge branch 'linux-next' of git://git.kernel.org/pub/scm/linux/kernel/git/jbarnes/pci 2012-01-11 18:50:26 -08:00
digsig.c lib/digsig: checks for NULL return value 2012-02-02 00:24:04 +11:00
div64.c
dma-debug.c Fix comparison using wrong pointer variable in dma debug code 2011-11-21 11:35:37 +01:00
dump_stack.c
dynamic_debug.c Merge branch 'driver-core-next' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core 2011-10-25 12:13:59 +02:00
dynamic_queue_limits.c dql: Dynamic queue limits 2011-11-29 12:46:19 -05:00
extable.c
fault-inject.c switch debugfs to umode_t 2012-01-03 22:54:56 -05:00
find_last_bit.c bitops: add #ifndef for each of find bitops 2011-05-26 17:12:38 -07:00
find_next_bit.c arch: remove CONFIG_GENERIC_FIND_{NEXT_BIT,BIT_LE,LAST_BIT} 2011-05-26 17:12:38 -07:00
flex_array.c flex_array: avoid divisions when accessing elements 2011-05-26 17:12:33 -07:00
gcd.c
gen_crc32table.c
genalloc.c lib, Make gen_pool memory allocator lockless 2011-08-03 11:15:57 -04:00
halfmd4.c
hexdump.c lib: add error checking to hex2bin 2011-09-20 23:24:44 -04:00
hweight.c
idr.c ida: make ida_simple_get/put() IRQ safe 2011-11-02 16:07:00 -07:00
inflate.c
int_sqrt.c
iomap_copy.c
iomap.c lib: add GENERIC_PCI_IOMAP 2011-11-28 21:12:42 +02:00
iommu-helper.c
ioremap.c ACPI, APEI, Generic Hardware Error Source POLL/IRQ/NMI notification type support 2011-01-12 03:06:19 -05:00
irq_regs.c
is_single_threaded.c
kasprintf.c
Kconfig arch: fix ioport mapping on mips,sh 2012-02-07 14:32:24 -08:00
Kconfig.debug kmemleak: Add support for memory hotplug 2011-12-02 16:12:42 +00:00
Kconfig.kgdb
Kconfig.kmemcheck
klist.c
kobject_uevent.c driver-core: skip uevent generation when nobody is listening 2011-12-09 16:23:50 -08:00
kobject.c kobject: remove kset_find_obj_hinted() 2011-12-21 15:13:54 -08:00
kstrtox.c Reduce the number of expensive division instructions done by _parse_integer() 2012-02-09 10:09:30 -08:00
kstrtox.h lib/kstrtox: common code between kstrto*() and simple_strto*() functions 2011-10-31 17:30:56 -07:00
lcm.c lib/lcm.c: quiet sparse noise 2011-07-25 20:57:15 -07:00
libcrc32c.c
list_debug.c Expand CONFIG_DEBUG_LIST to several other list operations 2011-02-18 11:32:28 -08:00
list_sort.c
llist.c llist: Remove cpu_relax() usage in cmpxchg loops 2011-10-04 12:44:03 +02:00
locking-selftest-hardirq.h
locking-selftest-mutex.h
locking-selftest-rlock-hardirq.h
locking-selftest-rlock-softirq.h
locking-selftest-rlock.h
locking-selftest-rsem.h
locking-selftest-softirq.h
locking-selftest-spin-hardirq.h
locking-selftest-spin-softirq.h
locking-selftest-spin.h
locking-selftest-wlock-hardirq.h
locking-selftest-wlock-softirq.h
locking-selftest-wlock.h
locking-selftest-wsem.h
locking-selftest.c rcu: Fix unpaired rcu_irq_enter() from locking selftests 2011-05-26 09:42:19 -07:00
lru_cache.c lru_cache: use correct type in sizeof for allocation 2011-05-25 08:39:52 -07:00
Makefile lib: Fix multiple definitions of clz_tab 2012-02-02 10:34:23 +11:00
md5.c crypto: Move md5_transform to lib/md5.c 2011-08-06 18:32:45 -07:00
nlattr.c netlink: validate NLA_MSECS length 2011-11-04 17:47:34 -04:00
parser.c Fix common misspellings 2011-03-31 11:26:23 -03:00
pci_iomap.c lib: add NO_GENERIC_PCI_IOPORT_MAP 2012-01-31 23:19:47 +02:00
percpu_counter.c lib/percpu_counter.c: enclose hotplug only variables in hotplug ifdef 2011-10-31 17:30:56 -07:00
plist.c plist: Remove the need to supply locks to plist heads 2011-07-08 14:02:53 +02:00
prio_heap.c
prio_tree.c
proportions.c locking, lib/proportions: Annotate prop_local_percpu::lock as raw 2011-09-13 11:11:50 +02:00
radix-tree.c radix_tree: take radix_tree_path off stack 2012-01-12 20:13:12 -08:00
random32.c
ratelimit.c locking, printk: Annotate logbuf_lock as raw 2011-09-13 11:11:54 +02:00
rational.c
rbtree.c Export the augmented rbtree helper functions 2011-01-28 12:16:59 +10:00
reciprocal_div.c sch_red: Adaptative RED AQM 2011-12-08 19:52:43 -05:00
rwsem-spinlock.c locking, rwsem: Annotate inner lock as raw 2011-09-13 11:11:59 +02:00
rwsem.c locking, rwsem: Annotate inner lock as raw 2011-09-13 11:11:59 +02:00
scatterlist.c
sha1.c lib/sha1.c: quiet sparse noise about symbol not declared 2011-09-13 16:09:41 -07:00
show_mem.c arch, mm: filter disallowed nodes from arch specific show_mem functions 2011-05-25 08:39:03 -07:00
smp_processor_id.c sched: Wrap scheduler p->cpus_allowed access 2011-10-06 12:46:56 +02:00
sort.c
spinlock_debug.c lib/spinlock_debug.c: print owner on spinlock lockup 2011-10-31 17:30:56 -07:00
string_helpers.c
string.c lib/string.c: fix strim() semantics for strings that have only blanks 2011-10-31 17:30:56 -07:00
swiotlb.c swiotlb: Expose swiotlb_nr_tlb function to modules 2011-12-06 10:38:03 +00:00
syscall.c
test-kstrtox.c kstrtox: fix compile warnings in test 2011-04-14 16:06:54 -07:00
textsearch.c textsearch: doc - fix spelling in lib/textsearch.c. 2011-01-24 23:33:30 -08:00
timerqueue.c Fix common misspellings 2011-03-31 11:26:23 -03:00
ts_bm.c
ts_fsm.c
ts_kmp.c
uuid.c
vsprintf.c net: introduce and use netdev_features_t for device features sets 2011-11-16 17:43:10 -05:00