Rails Performance Tuning

Rails Performance Tuning Steven Soroka and Burke LibbeyWednesday, 23 November, 11

Overview • Database performance problems • (basic) Caching • Application performance • Helpful toolsWednesday, 23 November, 11

Database performanceWednesday, 23 November, 11

The two big offenders • n+1 queries • missing indexesWednesday, 23 November, 11

n+1 queries • Rails makes it easy to fall into this trap. • @users = User.where(...) • @users.each { |u| u.posts.... } • Use #includes to ﬁxWednesday, 23 November, 11

Missing indexes • Databases are not magic • Rule of thumb: If you’re searching/sorting by a column, index it. • This includes (especially!) foreign keys • CardinalityWednesday, 23 November, 11

Other database tweaks • composite indexes • primary key range instead of limit/offset • explain & force index • avoiding subselects • carefully sizing columns • using NOT NULL / :null => false • INSERT faster than UPDATEWednesday, 23 November, 11

Also Handy: • IdentityMap (Rails 3.1) • conﬁg.active_record.identity_map = true • IdentityMap is disabled by default and still in development • use with careWednesday, 23 November, 11

Caching • memoization • fragment caching • action caching • page caching • others...Wednesday, 23 November, 11

Memoization • For expensive method calls with a ﬁnite set of return values • ActiveSupport::Memoizable is deprecated. :(Wednesday, 23 November, 11

Fragment Caching • http://guides.rubyonrails.org/ caching_with_rails.html • conﬁg.action_controller.perform_caching = true • <% cache ‘slow_view’ do %> ... <% end %> • expire_fragment(slow_view)Wednesday, 23 November, 11

Application Performance • Object allocations • Tuning the GC • Background jobs • Avoid disk access at all costs • Don’t be stupidWednesday, 23 November, 11

Don’t be StupidWednesday, 23 November, 11

Object Allocations • Ruby’s Garbage Collector is BAD. • Don’t create objects you don’t need • Reuse objects to save mem alloc?Wednesday, 23 November, 11

Tuning the GC • Use REE. • Use these settings: • https://gist.github.com/841168 RUBY_HEAP_MIN_SLOTS=500000 RUBY_HEAP_SLOTS_INCREMENT=250000 RUBY_HEAP_SLOTS_GROWTH_FACTOR=1 RUBY_GC_MALLOC_LIMIT=50000000Wednesday, 23 November, 11

Avoid Disk Access L1 Cache 3 L2 14 RAM 250 Disk 41,000,000 Network 240,000,000Wednesday, 23 November, 11

Background Jobs • Delayed::Job (db-driven, slowish) • Resque (Redis-driven, fast)Wednesday, 23 November, 11

Tools • rack-bug • rack-perftools • NewRelic RPM • ...and many more: lsof, tcpdump, strace, ltrace, rbtrace, perftools, perftools.rb, gdb, gdb.rb, memprof, memprof.com, hotspots..Wednesday, 23 November, 11

Rack::Bug • Handy toolbar for devmode • https://github.com/brynary/rack-bugWednesday, 23 November, 11

Rack::Perftools • Demo!Wednesday, 23 November, 11

Questions?Wednesday, 23 November, 11

Rails Performance Tuning

by Burke Libbey on Nov 23, 2011

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Rails Performance Tuning — Presentation Transcript