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diff --git a/docs/performance/memory/basic_operations.md b/docs/performance/memory/basic_operations.md new file mode 100644 index 0000000000..276c38bc2e --- /dev/null +++ b/docs/performance/memory/basic_operations.md @@ -0,0 +1,82 @@ +# Basic operations + +## Opening the Memory tool + +Before Firefox 50, the Memory tool is not enabled by default. To enable +it, open the developer tool settings, and check the "Memory" box under +"Default Firefox Developer Tools": + +<iframe width="595" height="325" src="https://www.youtube.com/embed/qi-0CoCOXw" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe> + +From Firefox 50 onwards, the Memory tool is enabled by default. + +## Taking a heap snapshot + +To take a snapshot of the heap, click the "Take snapshot" button, or +the camera icon on the left: + + + +The snapshot will occupy the large pane on the right-hand side. On the +left, you'll see an entry for the new snapshot, including its +timestamp, size, and controls to save or clear this snapshot: + + + +## Clearing a snapshot + +To remove a snapshot, click the "X" icon: + + + +## Saving and loading snapshots + +If you close the Memory tool, all unsaved snapshots will be discarded. +To save a snapshot click "Save": + + + +You'll be prompted for a name and location, and the file will be saved +with an `.fxsnapshot` extension. + +To load a snapshot from an existing `.fxsnapshot` file, click the import +button, which looks like a rectangle with an arrow rising from it +(before Firefox 49, this button was labeled with the text +"Import\...\"): + + + +You'll be prompted to find a snapshot file on disk. + +## Comparing snapshots + +Starting in Firefox 45, you can diff two heap snapshots. The diff shows +you where memory was allocated or freed between the two snapshots. + +To create a diff, click the button that looks like a Venn diagram next +to the camera icon (before Firefox 47, this looked like a \"+/-\" icon): + + + +You'll be prompted to select the snapshot to use as a baseline, then +the snapshot to compare. The tool then shows you the differences between +the two snapshots: + +<iframe width="595" height="325" src="https://www.youtube.com/embed/3Ow-mdK6b2M" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture"></iframe> + + +::: {.note} +When you're looking at a comparison, you can't use the Dominators view +or the Tree Map view. +::: + +## Recording call stacks + +The Memory tool can tell you exactly where in your code you are +allocating memory. However, recording this information has a run-time +cost, so you must ask the tool to record memory calls *before* the +memory is allocated, if you want to see memory call sites in the +snapshot. To do this, check "Record call stacks" (before Firefox 49 +this was labeled "Record allocation stacks"): + + |