Denys Vlasenko
133fd9f5cd
vsprintf: further optimize decimal conversion ...
Previous code was using optimizations which were developed to work well
even on narrow-word CPUs (by today's standards). But Linux runs only on
32-bit and wider CPUs. We can use that.
First: using 32x32->64 multiply and trivial 32-bit shift, we can correctly
divide by 10 much larger numbers, and thus we can print groups of 9 digits
instead of groups of 5 digits.
Next: there are two algorithms to print larger numbers. One is generic:
divide by 1000000000 and repeatedly print groups of (up to) 9 digits.
It's conceptually simple, but requires an (unsigned long long) /
1000000000 division.
Second algorithm splits 64-bit unsigned long long into 16-bit chunks,
manipulates them cleverly and generates groups of 4 decimal digits. It so
happens that it does NOT require long long division.
If long is > 32 bits, division of 64-bit values is relatively easy, and we
will use the first algorithm. If long long is > 64 bits (strange
architecture with VERY large long long), second algorithm can't be used,
and we again use the first one.
Else (if long is 32 bits and long long is 64 bits) we use second one.
And third: there is a simple optimization which takes fast path not only
for zero as was done before, but for all one-digit numbers.
In all tested cases new code is faster than old one, in many cases by 30%,
in few cases by more than 50% (for example, on x86-32, conversion of
12345678). Code growth is ~0 in 32-bit case and ~130 bytes in 64-bit
case.
This patch is based upon an original from Michal Nazarewicz.
[akpm@linux-foundation.org: checkpatch fixes]
Signed-off-by: Michal Nazarewicz <mina86@mina86.com>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
Cc: Douglas W Jones <jones@cs.uiowa.edu>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-31 17:49:27 -07:00
mpi: Avoid using freed pointer in mpi_lshift_limbs()
2012-04-18 12:14:28 +10:00
lib/raid6: cleanup gen_syndrome function selection
2012-05-22 13:54:24 +10:00
XZ: Fix incorrect XZ_BUF_ERROR
2011-09-21 13:39:59 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
bug.h: add include of it to various implicit C users
2012-02-29 17:15:08 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib/bitmap.c: fix documentation for scnprintf() functions
2012-05-29 16:22:32 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
btree: export btree_get_prev() so modules can use btree_for_each
2012-01-10 16:30:49 -08:00
bugs, x86: Fix printk levels for panic, softlockups and stack dumps
2012-01-26 21:28:45 +01:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: Fix multiple definitions of clz_tab
2012-02-02 10:34:23 +11:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
Docs: wording: functions -> algorithm
2011-10-29 21:20:22 +02:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib/cpumask.c: remove __any_online_cpu()
2012-03-28 17:14:35 -07:00
lib: crc8: add new library module providing crc8 algorithm
2011-06-03 15:01:06 -04:00
crc32: add self-test code for crc32c
2012-03-23 16:58:38 -07:00
crc32: select an algorithm via Kconfig
2012-03-23 16:58:38 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
debugobjects: Fill_pool() returns void now
2012-04-18 13:38:48 +02:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
decompress_bunzip2: remove invalid vi modeline
2011-12-06 10:00:05 +01:00
treewide: Fix comment and string typo 'bufer'
2011-12-06 09:53:40 +01:00
unlzo: fix input buffer free
2012-01-12 20:13:13 -08:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib/digsig: checks for NULL return value
2012-02-02 00:24:04 +11:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
Remove useless get_driver()/put_driver() calls
2012-01-24 16:00:35 -08:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
Revert "dynamic_debug: remove unneeded includes"
2012-05-07 16:47:32 -07:00
dql: Fix undefined jiffies
2012-03-11 19:59:43 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
crc32: bolt on crc32c
2012-03-23 16:58:38 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
The following text was taken from the original review request:
2012-03-24 10:24:31 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
The following text was taken from the original review request:
2012-03-24 10:24:31 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
ddr: add LPDDR2 data from JESD209-2
2012-05-02 00:04:06 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
Merge branch 'generic-string-functions'
2012-05-26 16:57:16 -07:00
Merge branches 'x86-asm-for-linus', 'x86-cleanups-for-linus', 'x86-cpu-for-linus', 'x86-debug-for-linus' and 'x86-microcode-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
2012-05-23 10:09:50 -07:00
Revert "driver core: check start node in klist_iter_init_node"
2012-04-19 19:17:30 -07:00
kobject: fix the uncorrect comment
2012-05-07 16:51:19 -07:00
The following text was taken from the original review request:
2012-03-24 10:24:31 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib/kstrtox: common code between kstrto*() and simple_strto*() functions
2011-10-31 17:30:56 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
list_debug: WARN for adding something already in the list
2012-05-29 16:22:32 -07:00
Disintegrate and delete asm/system.h
2012-03-28 15:58:21 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lru_cache: use correct type in sizeof for allocation
2011-05-25 08:39:52 -07:00
Merge branch 'generic-string-functions'
2012-05-26 16:57:16 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: add NO_GENERIC_PCI_IOPORT_MAP
2012-01-31 23:19:47 +02:00
lib/percpu_counter.c: enclose hotplug only variables in hotplug ifdef
2011-10-31 17:30:56 -07:00
bug.h: add include of it to various implicit C users
2012-02-29 17:15:08 -05:00
prio_tree: introduce prio_set_parent()
2012-03-23 16:58:36 -07:00
locking, lib/proportions: Annotate prop_local_percpu::lock as raw
2011-09-13 11:11:50 +02:00
radix-tree: fix preload vector size
2012-05-29 16:22:33 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: Change mail address of Oskar Schirmer
2012-05-17 15:18:37 +02:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
sch_red: Adaptative RED AQM
2011-12-08 19:52:43 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
The following text was taken from the original review request:
2012-03-24 10:24:31 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
arch, mm: filter disallowed nodes from arch specific show_mem functions
2011-05-25 08:39:03 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
spinlock_debug: print kallsyms name for lock
2012-05-29 16:22:33 -07:00
lib: add support for stmp-style devices
2012-04-20 23:27:08 +02:00
The following text was taken from the original review request:
2012-03-24 10:24:31 -07:00
lib/string_helpers.c: make arrays static
2012-05-29 16:22:32 -07:00
word-at-a-time: make the interfaces truly generic
2012-05-26 11:33:40 -07:00
lib: Fix generic strnlen_user for 32-bit big-endian machines
2012-05-27 20:59:46 -07:00
swiotlb: print physical addresses consistently with other parts of kernel
2012-05-29 16:22:21 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
lib/test-kstrtox.c: mark const init data with __initconst instead of __initdata
2012-05-29 16:22:32 -07:00
The following text was taken from the original review request:
2012-03-24 10:24:31 -07:00
lib: reduce the use of module.h wherever possible
2012-03-07 15:04:04 -05:00
vsprintf: further optimize decimal conversion
2012-05-31 17:49:27 -07:00
133fd9f5cd