我使用mina部署rails web app，但总是有很多错误 这是我的mina日志的一部分
Using mini_magick (4.5.1)
Installing pg (0.18.4)
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
current directory: /var/www/sample_app/shared/bundle/ruby/2.3.0/gems/pg-0.18.4/ext
/usr/bin/ruby2.3 -r ./siteconf20160917-1997-acaacj.rb extconf.rb
Cannot allocate memory - /usr/bin/ruby2.3 -r ./siteconf20160917-1997-acaacj.rb extconf.rb 2>&1
Gem files will remain installed in /var/www/sample_app/tmp/build-14740431655892/vendor/bundle/ruby/2.3.0/gems/pg-0.18.4 for inspection.
Results logged to /var/www/sample_app/tmp/build-14740431655892/vendor/bundle/ruby/2.3.0/extensions/x86_64-linux/2.3.0/pg-0.18.4/gem_make.out
An error occurred while installing pg (0.18.4), and Bundler cannot continue.
Make sure that `gem install pg -v '0.18.4'` succeeds before bundling.
! ERROR: Deploy failed.
-----> Cleaning up build
Unlinking current
OK
Connection to IP closed.
! Command failed.
Failed with status 1 (4864)
我注意到Cannot allocate memory但是我使用top监视内存，只使用了大约50％（总共1G），而且我已经运行gem install pg -v '0.18.4'，安装pg成功。我可以使用gem list找到它。
如何解决？谢谢