Thanks for the clarifications, Jakob. On Tue, Nov 11, 2014 at 1:40 AM, Jakob Kummerow <jkumme...@chromium.org> wrote: > mksnapshot isn't intended for creating arbitrary snapshots, that's why it's > not exposed or documented. You are of course free to play around with it, > but you're pretty much on your own. > > For the record, Chrome does not create a Chrome-specific V8 snapshot > (AFAIK). > > Also, bear in mind that putting stuff into the snapshot is a tradeoff: > extracting things from the snapshot is (usually) faster than > parsing/compiling them from source, but on the other hand extracting a > bigger snapshot is obviously slower than extracting a smaller snapshot. So > V8 tries very carefully to only put the most important bits into the > snapshot, rather than anything that might potentially be used at some point. > > On Tue, Nov 11, 2014 at 7:29 AM, Louis Santillan <lpsan...@gmail.com> wrote: >> >> So if I'm reading the qt doc [0] and src/mksnapshot.cc [1] correctly, >> mksnapshot expects to be run like something like >> >> ./mksnapshot [optional v8 engine args] mystartup.js mysnapshot.cc >> >> where mystartup.js is a JS file that runs without error. I would >> expect mystartup.js to be a significant enough part of your app that >> you can measure its compilation during startup. It should also be >> composed of the "common" part of your app; the part of your app that >> must run as a prerequisite for all execution paths. For v8, that >> means it uses mksnapshot to build the JS built-in objects into the >> runtime startup of itself (a sort bootstrapping technique). It's a >> process that takes less than 5 ms on an Intel(R) Xeon(R) CPU E3-1240 >> V2 @ 3.40GHz. I would imagine it's a lot more beneficial in >> Chrome/Chromium where DOM and a bunch of UI, network, crypto, etc., >> takes multiple MBs to load. >> >> Where this gets interesting is when your mystartup.js depends on >> Native objects or Native code not built-in to v8 or JS built-ins. >> mksnapshot does not seem to take this into account. However, it >> appears, that if you modify src/mksnapshot.cc somewhere after here [2] >> but before [3], then your mystartup.js *CAN* depend (and compile >> against) Native code just as is done in samples/shell.cc [4] to load >> the print/read/load/quit/version Native code. You'll have to rebuild >> v8 and you'll have to get your source tree co-mingled with v8's >> tree/build process, but such is life. >> >> [0] http://qt-project.org/wiki/V8Snapshot >> [1] https://github.com/v8/v8/blob/master/src/mksnapshot.cc >> [2] >> https://github.com/v8/v8/blob/134ebca3d871784966ea068d06210d9fe70ec4ab/src/mksnapshot.cc#L370 >> [3] >> https://github.com/v8/v8/blob/134ebca3d871784966ea068d06210d9fe70ec4ab/src/mksnapshot.cc#L395 >> [4] >> https://github.com/v8/v8/blob/134ebca3d871784966ea068d06210d9fe70ec4ab/samples/shell.cc#L96 >> >> On Mon, Nov 10, 2014 at 7:06 PM, Flying Jester <foolkingcr...@gmail.com> >> wrote: >> > Snapshots are enabled all the time unless you expressly disable them >> > with >> > gyp. >> > >> > >> > On Monday, November 10, 2014 4:59:37 PM UTC-9, Chris E wrote: >> >> >> >> Hello all, >> >> >> >> I am trying to use v8 snapshots to improve the start-up time of a v8 >> >> application (like what chrome/chromium does), but I am unable to find >> >> sufficient documentation to understand and use this feature. >> >> >> >> I have looked at the following references, but it is still not clear to >> >> me >> >> exactly how to make the best use of snapshots for performance. >> >> https://developers.google.com/v8/embed >> >> http://qt-project.org/wiki/V8Snapshot >> >> >> >> The QT link seemed the most useful so can anyone verify the correctness >> >> of >> >> this reference? >> >> >> >> So basically we have to compile and run our JS application with an >> >> emulator and somehow generate the snapshot.cc using mksnapshot? >> >> If our JS application is large and has many features, how do we know >> >> how >> >> much of it should run before creating the snapshot? >> >> How is this snapshot affected by libraries (both C++ and JS) that get >> >> loaded dynamically? >> >> >> >> Also it sounds like we have to be careful that the snapshot is not >> >> 'stale' >> >> or outdated with respect to the code that we run to create the snapshot >> >> right? >> >> >> >> Thank you so much for the help and clarifications. >> > >> > -- >> > -- >> > v8-users mailing list >> > v8-users@googlegroups.com >> > http://groups.google.com/group/v8-users >> > --- >> > You received this message because you are subscribed to the Google >> > Groups >> > "v8-users" group. >> > To unsubscribe from this group and stop receiving emails from it, send >> > an >> > email to v8-users+unsubscr...@googlegroups.com. >> > For more options, visit https://groups.google.com/d/optout. >> >> -- >> -- >> v8-users mailing list >> v8-users@googlegroups.com >> http://groups.google.com/group/v8-users >> --- >> You received this message because you are subscribed to the Google Groups >> "v8-users" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to v8-users+unsubscr...@googlegroups.com. >> For more options, visit https://groups.google.com/d/optout. > > > -- > -- > v8-users mailing list > v8-users@googlegroups.com > http://groups.google.com/group/v8-users > --- > You received this message because you are subscribed to the Google Groups > "v8-users" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to v8-users+unsubscr...@googlegroups.com. > For more options, visit https://groups.google.com/d/optout.
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