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Revision 59a32e2ce5eb809967cac4e718bc527beca83c59 authored by Eric Dumazet on 23 March 2012, 22:02:53 UTC, committed by Linus Torvalds on 23 March 2012, 23:58:42 UTC 
proc: speed up /proc/stat handling
 
On a typical 16 cpus machine, "cat /proc/stat" gives more than 4096 bytes,
and is slow :

  # strace -T -o /tmp/STRACE cat /proc/stat | wc -c
  5826
  # grep "cpu " /tmp/STRACE
  read(0, "cpu  1949310 19 2144714 12117253"..., 32768) = 5826 <0.001504>

Thats partly because show_stat() must be called twice since initial
buffer size is too small (4096 bytes for less than 32 possible cpus)

Fix this by :

 1) Taking into account nr_irqs in the initial buffer sizing.

 2) Using ksize() to allow better filling of initial buffer.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Glauber Costa <glommer@parallels.com>
Cc: Russell King - ARM Linux <linux@arm.linux.org.uk>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: Paul Turner <pjt@google.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
1 parent b908243
Raw File
mkmakefile 
#!/bin/sh
# Generates a small Makefile used in the root of the output
# directory, to allow make to be started from there.
# The Makefile also allow for more convinient build of external modules

# Usage
# $1 - Kernel src directory
# $2 - Output directory
# $3 - version
# $4 - patchlevel


test ! -r $2/Makefile -o -O $2/Makefile || exit 0
# Only overwrite automatically generated Makefiles
# (so we do not overwrite kernel Makefile)
if test -e $2/Makefile && ! grep -q Automatically $2/Makefile
then
	exit 0
fi
if [ "${quiet}" != "silent_" ]; then
	echo "  GEN     $2/Makefile"
fi

cat << EOF > $2/Makefile
# Automatically generated by $0: don't edit

VERSION = $3
PATCHLEVEL = $4

lastword = \$(word \$(words \$(1)),\$(1))
makedir := \$(dir \$(call lastword,\$(MAKEFILE_LIST)))

ifeq ("\$(origin V)", "command line")
VERBOSE := \$(V)
endif
ifneq (\$(VERBOSE),1)
Q := @
endif

MAKEARGS := -C $1
MAKEARGS += O=\$(if \$(patsubst /%,,\$(makedir)),\$(CURDIR)/)\$(patsubst %/,%,\$(makedir))

MAKEFLAGS += --no-print-directory

.PHONY: all \$(MAKECMDGOALS)

all	:= \$(filter-out all Makefile,\$(MAKECMDGOALS))

all:
	\$(Q)\$(MAKE) \$(MAKEARGS) \$(all)

Makefile:;

\$(all): all
	@:

%/: all
	@:
EOF
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