hgeditor

revlog: use mmap by default is pre-population is available

Using mmap has a great impact of memory usage on server, and a good impact on
performance in multiple case. Now that we pre-populate memory mapping by
default, there is case where it using mmap is slower. So we use it by default
(if pre-population is available).

Further work to reduce the performance impact of the pre-population will be done
later.

Some benchmark below (using the same setup as 522b4d729e89):

As for 522b4d729e89 the impact on small repository like Mercurial or Pypy is
tiny, ~1% best. However for large repositories we see some performance
improvement without seeing the performance regression that we could have without
pre-populate.

##### For netbeans

### data-env-vars.name            = netbeans-2018-08-01-zstd-sparse-revlog
 ## benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # benchmark.variants.limit-rev  = 1
  # benchmark.variants.patch      = yes
no-mmap:     0.171579
mmap:        0.166311   (-3.07%, -0.01)
  # bin-env-vars.hg.flavor        = default
no-mmap:     0.170716
mmap:        0.165218   (-3.22%, -0.01)
  # benchmark.variants.patch      = no
  # benchmark.variants.rev        = tip
no-mmap:     0.140862
mmap:        0.137566   (-2.34%, -0.00)
 ## benchmark.name                                 = hg.command.unbundle
  # bin-env-vars.hg.flavor                         = rust
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
  # benchmark.variants.source                      = unbundle
no-mmap:     0.238038
mmap:        0.239912
no-populate: 0.cbd4c9  (+11.71%, +0.03)


#### For Mozilla

### data-env-vars.name            = mozilla-try-2019-02-18-ds2-pnm
  # benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = rust
  # bin-env-vars.hg.py-re2-module = default
  # benchmark.variants.limit-rev  = 1
  # benchmark.variants.patch      = yes
no-mmap:     0.258440
mmap:        0.237813   (-7.98%, -0.02)
  # benchmark.variants.limit-rev  = 10
no-mmap:     1.235323
mmap:        1.213578   (-1.76%, -0.02)
 ## benchmark.name                                 = hg.command.push
  # bin-env-vars.hg.flavor                         = rust
  # bin-env-vars.hg.py-re2-module                  = default
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
no-mmap:     4.790135
mmap:        4.668971   (-2.53%, -0.12)
no-populate: 4.841141   (+1.06%, +0.05)


### data-env-vars.name            = mozilla-try-2019-02-18-zstd-sparse-revlog
 ## benchmark.name                = hg.command.log
  # bin-env-vars.hg.flavor        = default
  # benchmark.variants.limit-rev  = 1000
  # benchmark.variants.rev        = tip
no-mmap:     0.206187
mmap:        0.197348   (-4.29%, -0.01)
 ## benchmark.name                                 = hg.command.push
  # bin-env-vars.hg.flavor                         = default
  # benchmark.variants.explicit-rev                = none
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.protocol                    = ssh
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
no-mmap:     4.768259
mmap:        4.798632
no-populate: 4.953295   (+3.88%, +0.19)
  # benchmark.variants.revs                        = any-100-extra-rev
no-mmap:     4.785946
mmap:        4.903618
no-populate: 5.014963   (+4.79%, +0.23)
 ## benchmark.name                                 = hg.command.unbundle
  # bin-env-vars.hg.flavor                         = default
  # benchmark.variants.issue6528                   = disabled
  # benchmark.variants.reuse-external-delta-parent = yes
  # benchmark.variants.revs                        = any-1-extra-rev
  # benchmark.variants.source                      = unbundle
no-mmap:     1.400121
mmap:        1.423411
no-populate: 1.585365  (+13.23%, +0.19)

#!/bin/sh
#
# This is an example of using HGEDITOR to create of diff to review the
# changes while committing.

# If you want to pass your favourite editor some other parameters
# only for Mercurial, modify this:
case "${EDITOR}" in
    "")
        EDITOR="vi"
        ;;
    emacs)
        EDITOR="$EDITOR -nw"
        ;;
    gvim|vim)
        EDITOR="$EDITOR -f -o"
        ;;
esac


HGTMP=""
cleanup_exit() {
    rm -rf "$HGTMP"
}

# Remove temporary files even if we get interrupted
trap "cleanup_exit" 0 # normal exit
trap "exit 255" HUP INT QUIT ABRT TERM

HGTMP=$(mktemp -d ${TMPDIR-/tmp}/hgeditor.XXXXXX)
[ x$HGTMP != x -a -d $HGTMP ] || {
  echo "Could not create temporary directory! Exiting." 1>&2
  exit 1
}

(
    grep '^HG: changed' "$1" | cut -b 13- | while read changed; do
        "$HG" diff "$changed" >> "$HGTMP/diff"
    done
)

cat "$1" > "$HGTMP/msg"

MD5=$(which md5sum 2>/dev/null) || \
    MD5=$(which md5 2>/dev/null)
[ -x "${MD5}" ] && CHECKSUM=`${MD5} "$HGTMP/msg"`
if [ -s "$HGTMP/diff" ]; then
    $EDITOR "$HGTMP/msg" "$HGTMP/diff" || exit $?
else
    $EDITOR "$HGTMP/msg" || exit $?
fi
[ -x "${MD5}" ] && (echo "$CHECKSUM" | ${MD5} -c >/dev/null 2>&1 && exit 13)

mv "$HGTMP/msg" "$1"

exit $?