<div xmlns="http://www.w3.org/1999/xhtml">Hi libvirt comuninty’s developers. I will try the fast explain. We’re working on kvm for a project and we tried get current machine’s memory usages. The code we tried to use for this operation is as shown in the below. irb(main):002:0> conn = Libvirt::open("qemu:///system")=> #<Libvirt::Connect:0x000055d1c66de398>irb(main):003:0> domain = conn.lookup_domain_by_name("2_2").memory_stats=> [#<Libvirt::Domain::MemoryStats:0x000055d1c6621a68 @tag=6, @val=1048576>, #<Libvirt::Domain::MemoryStats:0x000055d1c6621978 @tag=7, @val=1180796>]irb(main):004:0> domain.first.valTraceback (most recent call last):16: from /root/.rbenv/versions/2.5.1/bin/bundle:23:in `load'15: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/exe/bundle:22:in `<top (required)>'14: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/friendly_errors.rb:124:in `with_friendly_errors'13: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/exe/bundle:30:in `block in <top (required)>'12: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli.rb:18:in `start'11: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor/base.rb:466:in `start'10: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli.rb:27:in `dispatch'9: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor.rb:387:in `dispatch'8: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor/invocation.rb:126:in `invoke_command'7: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/vendor/thor/lib/thor/command.rb:27:in `run'6: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli.rb:424:in `exec'5: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli/exec.rb:28:in `run'4: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli/exec.rb:74:in `kernel_load'3: from /root/.rbenv/versions/2.5.1/lib/ruby/gems/2.5.0/gems/bundler-1.16.6/lib/bundler/cli/exec.rb:74:in `load'2: from bin/console:13:in `<top (required)>'1: from (irb):4NoMethodError (undefined method `val' for #<Libvirt::Domain::MemoryStats:0x000055d1c6621a68>)Did you mean? valueirb(main):005:0> domain.first.value=> nil As you see, when we want the use memory_usage’s val parameter but Libvirt throwing up undefined method error. Our fix proffer is memory_stats function's return @val parameter enough be update as shown in the below.diff --git a/ext/libvirt/domain.c b/ext/libvirt/domain.cindex d665907..d458e98 100644--- a/ext/libvirt/domain.c+++ b/ext/libvirt/domain.c@@ -675,7 +675,7 @@ static VALUE libvirt_domain_memory_stats(int argc, VALUE *argv, VALUE d)for (i = 0; i < r; i++) {tmp = rb_class_new_instance(0, NULL, c_domain_memory_stats);rb_iv_set(tmp, "@tag", INT2NUM(stats[i].tag));- rb_iv_set(tmp, "@val", ULL2NUM(stats[i].val));+ rb_iv_set(tmp, "@value", ULL2NUM(stats[i].val)); rb_ary_store(result, i, tmp);} After that change memory_stats method’s val error will solved as shown in the below. irb(main):002:0> conn = Libvirt::open("qemu:///system")=> #<Libvirt::Connect:0x0000562ecf943320>irb(main):003:0> memory_stats = conn.lookup_domain_by_name("2_2").memory_stats=> [#<Libvirt::Domain::MemoryStats:0x0000562ecf976f68 @tag=6, @value=1048576>, #<Libvirt::Domain::MemoryStats:0x0000562ecf976f40 @tag=7, @value=1182952>]irb(main):004:0> memory_stats.first.value=> 1048576</div>