{"id":1946,"date":"2012-05-30T17:18:17","date_gmt":"2012-05-30T06:18:17","guid":{"rendered":"http:\/\/blog.mozilla.org\/nnethercote\/?p=1946"},"modified":"2012-05-31T11:40:15","modified_gmt":"2012-05-31T00:40:15","slug":"memshrink-progress-week-49-50","status":"publish","type":"post","link":"https:\/\/blog.mozilla.org\/nnethercote\/2012\/05\/30\/memshrink-progress-week-49-50\/","title":{"rendered":"MemShrink progress, week 49-50"},"content":{"rendered":"

System Compartment Reporting<\/h3>\n

With the recent landing of compartment-per-global, Firefox now regularly has 200+ system compartments at start-up.\u00a0 However, most of these compartments didn’t have names, which meant that they were merged into a single “[System Principal]” entry in about:memory and about:compartments.<\/p>\n

Until last week, that is, when Nils Maier added identifying information to the vast majority of these<\/a>.\u00a0 Here’s a small selection of interesting ones from about:compartments on my own machine.<\/p>\n

about:blank\r\nabout:compartments\r\nabout:memory?verbose\r\n\r\nchrome:\/\/adblockplus-modules\/content\/FilterClasses.jsm\r\n\r\nchrome:\/\/browser\/content\/bookmarks\/bookmarksPanel.xul\r\nchrome:\/\/browser\/content\/browser.xul\r\nchrome:\/\/browser\/content\/places\/menu.xml\r\nchrome:\/\/browser\/content\/search\/search.xml\r\n\r\nchrome:\/\/chatzilla\/content\/browserOverlay.xul\r\n\r\nchrome:\/\/global\/content\/bindings\/button.xml\r\nchrome:\/\/global\/content\/globalOverlay.xul\r\n\r\nchrome:\/\/treestyletab\/content\/treestyletab.xul\r\n\r\nfile:\/\/\/home\/njn\/moz\/mi0\/o64\/dist\/bin\/components\/TelemetryPing.js\r\n\r\njar:file:\/\/\/home\/njn\/moz\/mi0\/o64\/dist\/bin\/extensions\/uriloader@pdf.js.xpi!\/bootstrap.js\r\njar:file:\/\/\/home\/njn\/moz\/mi0\/o64\/dist\/bin\/extensions\/uriloader@pdf.js.xpi!\/components\/PdfStreamConverter.js\r\n\r\nresource:\/\/\/modules\/TelemetryTimestamps.jsm\r\nresource:\/\/\/modules\/sessionstore\/DocumentUtils.jsm\r\n\r\nresource:\/\/gre-resources\/hiddenWindow.html\r\n\r\nresource:\/\/gre\/modules\/AddonManager.jsm\r\n\r\nresource:\/\/services-common\/preferences.js\r\nresource:\/\/services-crypto\/WeaveCrypto.js\r\nresource:\/\/services-sync\/constants.js\r\nresource:\/\/services-sync\/engines\/bookmarks.js\r\n\r\nresource:\/\/treestyletab-modules\/browser.js\r\nresource:\/\/treestyletab-modules\/lib\/animationManager.js<\/pre>\n
Just from this, it’s obvious that I had about:compartments and about:memory?verbose open at the time.\u00a0 It’s also obvious that I had the following add-ons installed:\u00a0 AdBlock Plus, Chatzilla, Tree Style Tab, and pdf.js.\u00a0 And about:memory now gives at least a partial measurement of how much memory these add-ons are using.\u00a0 This will help identify add-ons that are using excessive amounts of memory.\u00a0 (Having said that, I identified the add-on compartments simply by their names.\u00a0 It’d be great if there was a way to systematically identify them within the code, but I don’t know if that’s possible.)<\/p>\n
I also hope people will scrutinize Firefox’s own compartment use closely, and start to file bug reports saying things like “hey, that .jsm module shouldn’t be present, there must be a leak”.\u00a0 If you want to see what the full list of 200+ looks like, try out a recent Nightly build!<\/p>\n
In related news, I also added some new compartment-specific reports<\/a>, including ones for cross-compartment wrappers.<\/p>\n
One consequence of all these change is that the number of entries in about:memory jumped tremendously.\u00a0 As a result, I aggregated the small entries within each compartment<\/a>, which reduces the number of entries by a factor of roughly four while still reporting full information for large compartments.\u00a0 Nils and I also made about:memory<\/a> more efficient<\/a>, so the amount of memory required to generate each line dropped by about 20%.\u00a0 about:memory still takes up memory itself, but it does so at a level that I’m fairly happy with.<\/p>\n
Add-ons<\/h3>\n
For a change, the biggest MemShrink-related news in this report wasn’t related to add-ons!\u00a0 But there was still some interesting movement there.<\/p>\n
Justin Lebar uncovered some evidence that the Hueyfix<\/a> is having a real, positive effect among users.\u00a0 Telemetry data from Nightly users shows that the number of ghost windows — a concept for which we don’t have good documentation, but they correlate with zombie compartments — has dropped dramatically, as the following graph shows.<\/p>\n
\"ghost<\/a><\/p>\n
Telemetry data tends to be extremely noisy, so it’s nice to see a clear signal — Kyle’s change made it into Nightly builds on May 5th [Update:<\/strong> that’s incorrect, see below] and immediately caused the mean number of ghost windows to drop from roughly three to roughly one.\u00a0 The variance also dropped dramatically.<\/p>\n
Update:<\/strong> Justin just wrote a blog post<\/a> that explains very nicely what ghost windows are.\u00a0 That post also explains better the circumstances behind the drop in ghost window numbers;\u00a0 my explanation above was too simple and got the timing wrong.\u00a0 Thanks, Justin!<\/p>\n
In other add-on news, the following add-ons had leaks fixed: Readability<\/a>, ProxTube<\/a>, Youtube MP3 Podcaster.<\/p>\n
Firefox vs The New York Times<\/h3>\n
Robert O’Callahan fixed a leak relating to mouse events<\/a> that triggered when he visited nytimes.com.\u00a0 He wrote\u00a0a great blog post<\/a> explaining the heroic debugging — searching through full memory dumps! — that was required.\u00a0 It’s great that Robert found and fixed this, though it’s a shame it took such expertise.<\/p>\n
Bug Counts<\/h3>\n
Here are the current bug counts.<\/p>\n
    \n
  • P1: 23 (-1\/+2)<\/li>\n
  • P2: 85 (-2\/+4)<\/li>\n
  • P3: 102 (-5\/+2)<\/li>\n
  • Unprioritized: 2 (-3\/+2)<\/li>\n<\/ul>\n
    Not a great deal of movement.\u00a0 We only had to triage twelve bugs in today’s MemShrink meeting, which is the fewest we’ve had since we switched to fortnightly meetings.<\/p>\n","protected":false},"excerpt":{"rendered":"
    System Compartment Reporting With the recent landing of compartment-per-global, Firefox now regularly has 200+ system compartments at start-up.\u00a0 However, most of these compartments didn’t have names, which meant that they were merged into a single “[System Principal]” entry in about:memory and about:compartments. Until last week, that is, when Nils Maier added identifying information to the […]<\/p>\n","protected":false},"author":139,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[15267,4550,4559,119,4554,30,4544,4546],"tags":[],"_links":{"self":[{"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/posts\/1946"}],"collection":[{"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/users\/139"}],"replies":[{"embeddable":true,"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/comments?post=1946"}],"version-history":[{"count":0,"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/posts\/1946\/revisions"}],"wp:attachment":[{"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/media?parent=1946"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/categories?post=1946"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/blog.mozilla.org\/nnethercote\/wp-json\/wp\/v2\/tags?post=1946"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}