RasPiで作業をしていると、もう少しだけメモリがほしいと思うことがあります（ウソ）。
だいたい、RasPi3だと1GBのメモリがあるんだから、普通は足らないことはないです。
ちょっと遅くなっても良ければ、swapを増やせばいいですし、、、
なので、メモリが足らない状態というのは、道を外れた時に限ります！（決めつけ）
0.設定を変更する前、ログイン直後のfreeの結果
pi@raspberrypi:~ $ free -h
total used free shared buffers cached
Mem: 923M 69M 854M 6.2M 6.6M 34M
-/+ buffers/cache: 28M 895M
Swap: 99M 0B 99M
pi@raspberrypi:~ $
1.GPUに64MBもいらないって!
てっとり早いのはGPUに割り当てられているメモリを少なくする方法ですね。
pi@raspberrypi:~ $ sudo raspi-config
1 Change User Password Change password for the default u
2 Hostname Set the visible name for this Pi
3 Boot Options Configure options for start-up
4 Localisation Options Set up language and regional sett
5 Interfacing Options Configure connections to peripher
6 Overclock Configure overclocking for your P
7 Advanced Options Configure advanced settings
8 Update Update this tool to the latest ve
9 About raspi-config Information about this configurat
<Select> <Finish>
7 Advanced Optionsを選択します。
A1 Expand Filesystem Ensures that all of the SD card s
A2 Overscan You may need to configure oversca
A3 Memory Split Change the amount of memory made
A4 Audio Force audio out through HDMI or 3
A5 Resolution Set a specific screen resolution
A6 GL Driver Enable/Disable experimental deskt
<Select> <Back>
A3 Memory Splitを選択します。
How much memory should the GPU have? e.g. 16/32/64/128/256
64________________________________________________________________
<Ok> <Cancel>
初期値の64MBを16MBにしましょう。再起動すると、、、
pi@raspberrypi:~ $ free -h
total used free shared buffers cached
Mem: 970M 69M 901M 6.5M 6.6M 34M
-/+ buffers/cache: 28M 942M
Swap: 99M 0B 99M
pi@raspberrypi:~ $
おー、Totalが923MBから970MBになってます。ん？47MB増えたの？1MBはどこへ？
2.swap止めちゃう？
pi@raspberrypi:~ $ sudo dphys-swapfile swapoff
pi@raspberrypi:~ $
再起動して
pi@raspberrypi:~ $ free -h
total used free shared buffers cached
Mem: 970M 69M 901M 6.5M 6.6M 34M
-/+ buffers/cache: 28M 942M
Swap: 99M 0B 99M
pi@raspberrypi:~ $
あれ？増えてない。
3.サービス止めちゃう？
ひとまず、chkconfigをインストールしましょう。
pi@raspberrypi:~ $ sudo apt-get install chkconfig
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following NEW packages will be installed:
chkconfig
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 0 B/9766 B of archives.
After this operation, 59.4 kB of additional disk space will be used.
Selecting previously unselected package chkconfig.
(Reading database ... 31532 files and directories currently installed.)
Preparing to unpack .../chkconfig_11.4.54.60.1debian1_all.deb ...
Unpacking chkconfig (11.4.54.60.1debian1) ...
Processing triggers for man-db (2.7.5-1~bpo8+1) ...
Setting up chkconfig (11.4.54.60.1debian1) ...
pi@raspberrypi:~ $
動作しているサービスは、、、
pi@raspberrypi:~ $ chkconfig --list
alsa-utils 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
avahi-daemon 0:off 1:off 2:on 3:on 4:on 5:on 6:off
bluetooth 0:off 1:off 2:on 3:on 4:on 5:on 6:off
bootlogs 0:off 1:on 2:on 3:on 4:on 5:on 6:off
bootmisc.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
checkfs.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
checkroot-bootclean.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
checkroot.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
console-setup 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
cron 0:off 1:off 2:on 3:on 4:on 5:on 6:off
dbus 0:off 1:off 2:on 3:on 4:on 5:on 6:off
dhcpcd 0:off 1:off 2:on 3:on 4:on 5:on 6:off
dphys-swapfile 0:off 1:off 2:on 3:on 4:on 5:on 6:off
fake-hwclock 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
hostname.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
hwclock.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off
kbd 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
keyboard-setup 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
killprocs 0:off 1:on 2:off 3:off 4:off 5:off 6:off
kmod 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
motd 0:off 1:on 2:on 3:on 4:on 5:on 6:off
mountall-bootclean.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
mountall.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
mountdevsubfs.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
mountkernfs.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
mountnfs-bootclean.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
mountnfs.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
networking 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
nfs-common 0:off 1:off 2:off 3:off 4:off 5:off 6:off
ntp 0:off 1:off 2:on 3:on 4:on 5:on 6:off
plymouth 0:off 1:off 2:on 3:on 4:on 5:on 6:off
plymouth-log 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
procps 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
raspi-config 0:off 1:off 2:on 3:on 4:on 5:on 6:off S:on
rc.local 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rcS 0:off 1:off 2:off 3:off 4:off 5:off 6:off
rmnologin 0:off 1:off 2:on 3:on 4:on 5:on 6:off
rpcbind 0:off 1:off 2:off 3:off 4:off 5:off 6:off
rsyslog 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sendsigs 0:off 1:off 2:off 3:off 4:off 5:off 6:off
ssh 0:off 1:off 2:on 3:on 4:on 5:on 6:off
sudo 0:off 1:off 2:off 3:off 4:off 5:off 6:off
triggerhappy 0:off 1:off 2:on 3:on 4:on 5:on 6:off
udev 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
udev-finish 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
umountfs 0:off 1:off 2:off 3:off 4:off 5:off 6:off
umountnfs.sh 0:off 1:off 2:off 3:off 4:off 5:off 6:off
umountroot 0:off 1:off 2:off 3:off 4:off 5:off 6:off
urandom 0:off 1:off 2:off 3:off 4:off 5:off 6:off S:on
pi@raspberrypi:~ $
いらなさそうなの止めちゃいましょう(自己責任で)
sudo chkconfig avahi-daemon off
sudo chkconfig bluetooth off
sudo chkconfig cron off
sudo chkconfig dbus off
sudo chkconfig dhcpcd off
sudo chkconfig dphys-swapfile off
sudo chkconfig motd off
sudo chkconfig ntp off
sudo chkconfig plymouth off
sudo chkconfig triggerhappy off
dhcpcdやntpを止めるとまずいことが多いですが、固定IPアドレスにしたり、時間にこだわらないときは止めちゃいましょう。再起動してすると
pi@raspberrypi:~ $ free -h
total used free shared buffers cached
Mem: 970M 67M 903M 6.5M 6.6M 33M
-/+ buffers/cache: 27M 943M
Swap: 0B 0B 0B
pi@raspberrypi:~ $
マジか！freeが2MBだけ増えてる。ついでにswapもゼロになってます。
ただ、手間の割には、んーーーーー。まあ、増えたのは事実。
参考にさせていただいたのはコチラ
メモのページ - チラシの裏メモ 別紙
http://d.hatena.ne.jp/debslink/20160827/1472285472