On 02/10/2015 11:11 AM, Erdal Mutlu wrote:
On Tuesday, February 10, 2015 at 6:59:20 PM UTC+2, Steve Fink wrote:
On 02/10/2015 01:06 AM, Erdal Mutlu wrote:
Hi,
I have been instrumenting the JS engine interpreter for logging memory updates
on JS scripts. My current instrumentation logs every use of the interpreter for
script execution which also includes browser (internal) script execution. I
wanted to ask if there is a way to separate these internal calls from the user
(webpage) specific scripts running on the interpreter.
I couldn't be sure if this question should be directed to platform or js-engine
so I am posting it to both. Thanks in advance.
There's actually another list called js-engine. You're posting to
js-engine-internals, which is fine (and better than dev-platform).
I do not completely understand your question. You say you are logging
"memory updates on JS scripts", but then you discuss logging script
executions. I'm not sure if you just want to log script invocations,
categorized by content vs internal, or if you are just doing that in
order to categorize memory accesses.
All scripts live within a compartment, and you can tell from that
compartment whether the script is from content (user/webpage) or chrome
(browser/internal). Not only that, but all memory allocations that are
managed by the JS engine's garbage collector (we call them GC things)
are also contained with a compartment. There is other memory which may
be either controlled by a GC thing (as in, it will be automatically
freed when that GC thing is no longer live), or is completely external
to the GC. Those are harder to associate with content vs chrome. This is
what about:memory does -- it scans through all (well, most) of allocated
memory and categorizes it when possible, or else puts it an "Other"
category when it is not directly associated with a web page or chrome.
Logging script execution crossings between content and chrome is another
matter, since it is about control flow. It's relatively easy to do if
you're only running in the interpreter, since you have to "enter" a
compartment in order to create or manipulate anything. You can
instrument those compartment entries. But I think the JITs do some
compartment-crossing internally, and that's harder to track. (You can
always run with the JITs disabled if that will work for whatever it is
you are trying to accomplish.)
If you tell me more about what exactly you are trying to achieve, we
could probably be more helpful.
Thanks for the quick response and insight about the compartments.
I've been working on a scheme to record the memories accessed during the
execution of JS script. So far I have been adding some logging mechanism on the
Interpret function (namely JSOP_GETNAME, JSOP_GETPROP, JSOP_SETNAME,
JSOP_SETPROP). Basically, I am recording the values read and written to JS
variables and properties.
But I only want to record these values for scripts from content rather than
chrome.
Ah, then Jan was right.
Use cx->compartment()->isSystem()
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