store: don't read the whole fncache in memory
In large repositories with lot of files, the fncache grows more than 100 MB and
reading that whole thing into memory slows things down. Let's not read the whole
thing into memory.
This patch changes fncache loading code to read 1 MB at once. Loading 1 MB at
once saves ~1 sec on perffncacheload for our internal repository. I tried
various values such as 0.5 MB, 5 MB, 10 MB but best results were produced using
1 MB as the chunksize.
On a narrow clone with fncache around 40 MB, this patch saves ~0.04 seconds on
average on perffncacheload.
To test the code, I have coded an extension in test-fncache.t which set
chunksize to 1 byte, and the test passes with that.
Differential Revision: https://phab.mercurial-scm.org/D5296
# Extract version number into 4 parts, some of which may be empty:
#
# version: the numeric part of the most recent tag. Will always look like 1.3.
#
# type: if an rc build, "rc", otherwise empty
#
# distance: the distance from the nearest tag, or empty if built from a tag
#
# node: the node|short hg was built from, or empty if built from a tag
gethgversion() {
export HGRCPATH=
export HGPLAIN=
make cleanbutpackages
make local PURE=--pure
HG="$PWD/hg"
"$HG" version > /dev/null || { echo 'abort: hg version failed!'; exit 1 ; }
hgversion=`LANGUAGE=C "$HG" version | sed -ne 's/.*(version \(.*\))$/\1/p'`
if echo $hgversion | grep + > /dev/null 2>&1 ; then
tmp=`echo $hgversion | cut -d+ -f 2`
hgversion=`echo $hgversion | cut -d+ -f 1`
distance=`echo $tmp | cut -d- -f 1`
node=`echo $tmp | cut -d- -f 2`
else
distance=''
node=''
fi
if echo $hgversion | grep -E -- '[0-9]\.[0-9](\.[0-9])?rc' > /dev/null 2>&1; then
version=`echo $hgversion | cut -d'r' -f1`
type="rc`echo $hgversion | cut -d'c' -f2-`"
else
version=$hgversion
type=''
fi
}