Re: [v8-users] Re: V8 snapshots

[Zac Hansen]

can you make a special code path just for making the snapshot that releases
the persistent/globals then makes the snapshots and then exits?   Then you
start up the "normal" code pay with the new snapshots that can create the
persistent a/globals all it wants.

On Thu, Sep 7, 2017 at 1:33 PM Francisco Moraes 
wrote:

> Thanks. I am finding that my main hurdle is that there are several
> v8::Persistent objects which block creation of the snapshot. Is there any
> suggested work around for those other than rewriting the code ?
>
>
> On Thursday, September 7, 2017 at 11:16:24 AM UTC-4, Jakob Gruber wrote:
>>
>> You can use the `job` gdb macro (see gdbinit
>> )
>> to print heap objects. E.g. 'job 0x367b6c023fa9'.
>>
>>
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Re: [v8-users] Re: V8 snapshots

[Francisco Moraes]

Thanks. I am finding that my main hurdle is that there are several 
v8::Persistent objects which block creation of the snapshot. Is there any 
suggested work around for those other than rewriting the code ?


On Thursday, September 7, 2017 at 11:16:24 AM UTC-4, Jakob Gruber wrote:
>
> You can use the `job` gdb macro (see gdbinit 
> )
>  
> to print heap objects. E.g. 'job 0x367b6c023fa9'.
>
>
>

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Re: [v8-users] Re: V8 snapshots

[Zac Hansen]

Just a guess but how would he system know how to deal with objects held by
global handles when making a snapshot?   You can't serialize the global
handles in such a way that they would be useful in any way?

I'm guessing this is just a sanity check to make sure you aren't doing
something unintended.

I could be completely wrong but I'd say just free up your globals and if
that changes the behavior then you weren't ready to make a snapshot anyhow.


On Wed, Sep 6, 2017 at 11:27 AM Francisco Moraes 
wrote:

> After fixing the issue about the handle scope, I can successfully create
> the snapshot for the test code, but when I tried something more
> complicated, I ran into this now:
>
> Check failed: 0 == isolate->global_handles()->global_handles_count() (0
> vs. 4).
>
>
> On Wednesday, September 6, 2017 at 12:27:35 PM UTC-4, Zac Hansen wrote:
>>
>>
>> https://v8.paulfryzel.com/docs/master/classv8_1_1_snapshot_creator.html#a86b2023acdb88a9bd6eae2695f2b0a8a
>>
>> Created a snapshot data blob. This must not be called from within a
>> handle scope.
>>
>>
>>
>>
>> On Wednesday, September 6, 2017 at 7:20:33 AM UTC-7, Francisco Moraes
>> wrote:
>>>
>>> Here's a simple recreate that I managed to create:
>>>
>>> #include 
>>>
>>> #include "v8.h"
>>> #include "libplatform/libplatform.h"
>>>
>>> int main(int argv, char **argc)
>>> {
>>> const char *v8flags = "";
>>> v8::Platform *platform = v8::platform::CreateDefaultPlatform();
>>> v8::V8::SetFlagsFromString (v8flags, strlen (v8flags));
>>> v8::V8::InitializePlatform(platform);
>>> v8::V8::Initialize();
>>>
>>> v8::SnapshotCreator creator;
>>> v8::Isolate *isolate = creator.GetIsolate();
>>>
>>> v8::HandleScope handle_scope(isolate);
>>> v8::Local context = v8::Context::New(isolate);
>>> const char* source = "function initialize(obj) { return true; }";
>>> v8::Context::Scope context_scope(context);
>>> v8::TryCatch try_catch(isolate);
>>> v8::Local source_string;
>>> v8::String::NewFromUtf8(isolate, source, v8::NewStringType::kNormal)
>>> .ToLocal(_string);
>>> v8::ScriptOrigin origin =
>>> v8::ScriptOrigin(v8::String::NewFromUtf8(isolate, "testscript"));
>>> v8::ScriptCompiler::Source sourcecode(source_string, origin);
>>> v8::Local script;
>>> bool success = v8::ScriptCompiler::Compile(context,
>>> ).ToLocal();
>>>
>>> script->Run(context);
>>>
>>> creator.SetDefaultContext(context);
>>> v8::StartupData blob =
>>> creator.CreateBlob(v8::SnapshotCreator::FunctionCodeHandling::kClear);
>>>
>>> return 1;
>>> }
>>>
>>> The interesting thing is if I call v8::V8::CreateSnapshotDataBlob it
>>> works as it does all the above work for me, so something in trying to use
>>> the SnapshotCreator is causing me some issue as I will need to handle
>>> custom embedder fields, etc...
>>>
>>> On Tuesday, September 5, 2017 at 2:50:36 PM UTC-4, Zac Hansen wrote:

 That kind of error usually means you either haven't created a context
 or aren't in a context or haven't created an appropriate handle.  Or...
 Something else :-/. Maybe a lock?  V8 errors are very much a "you screwed
 up somewhere" notification and often nothing more

 On Tue, Sep 5, 2017 at 9:42 AM Francisco Moraes 
 wrote:

> I will give it a try sometime this week. I tried to remove our
> initialization JS file but that caused a failure further down the
> serialization as well, so still investigating.
>
>
> On Saturday, September 2, 2017 at 1:07:28 AM UTC-4, Zac Hansen wrote:
>>
>> Can you post a minimal complete example that reproduces your problem?
>>
>> On Friday, September 1, 2017 at 8:57:51 AM UTC-7, Francisco Moraes
>> wrote:
>>>
>>> Hello,
>>>
>>> I am trying to create a snapshot that includes most of code but I
>>> ran into the following assertion:
>>>
>>>   CHECK(isolate->handle_scope_implementer()->blocks()->is_empty());
>>>
>>> Any clarifications about what would generate it that our JS code is
>>> doing and is not legal? I found that creating Unsafe Arrays is also not
>>> permitted but that is relatively easy to work around.
>>>
>>> Francisco
>>>
>> --
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>>> On Tuesday, September 5, 2017 at 2:50:36 PM UTC-4, Zac Hansen wrote:

 That kind of error usually means you either haven't created a 

Re: [v8-users] Re: V8 snapshots

[Zac Hansen]

https://v8.paulfryzel.com/docs/master/classv8_1_1_snapshot_creator.html#a86b2023acdb88a9bd6eae2695f2b0a8a

Created a snapshot data blob. This must not be called from within a handle 
scope.




On Wednesday, September 6, 2017 at 7:20:33 AM UTC-7, Francisco Moraes wrote:
>
> Here's a simple recreate that I managed to create:
>
> #include 
>
> #include "v8.h"
> #include "libplatform/libplatform.h"
>
> int main(int argv, char **argc)
> {
> const char *v8flags = "";
> v8::Platform *platform = v8::platform::CreateDefaultPlatform();
> v8::V8::SetFlagsFromString (v8flags, strlen (v8flags));
> v8::V8::InitializePlatform(platform);
> v8::V8::Initialize();
>
> v8::SnapshotCreator creator;
> v8::Isolate *isolate = creator.GetIsolate();
> 
> v8::HandleScope handle_scope(isolate);
> v8::Local context = v8::Context::New(isolate);
> const char* source = "function initialize(obj) { return true; }";
> v8::Context::Scope context_scope(context);
> v8::TryCatch try_catch(isolate);
> v8::Local source_string;
> v8::String::NewFromUtf8(isolate, source, v8::NewStringType::kNormal)
> .ToLocal(_string);
> v8::ScriptOrigin origin = 
> v8::ScriptOrigin(v8::String::NewFromUtf8(isolate, "testscript"));
> v8::ScriptCompiler::Source sourcecode(source_string, origin);
> v8::Local script;
> bool success = v8::ScriptCompiler::Compile(context, 
> ).ToLocal();
>
> script->Run(context);
>   
> creator.SetDefaultContext(context);
> v8::StartupData blob = 
> creator.CreateBlob(v8::SnapshotCreator::FunctionCodeHandling::kClear);
>
> return 1;
> }
>
> The interesting thing is if I call v8::V8::CreateSnapshotDataBlob it works 
> as it does all the above work for me, so something in trying to use the 
> SnapshotCreator is causing me some issue as I will need to handle custom 
> embedder fields, etc...
>
> On Tuesday, September 5, 2017 at 2:50:36 PM UTC-4, Zac Hansen wrote:
>>
>> That kind of error usually means you either haven't created a context or 
>> aren't in a context or haven't created an appropriate handle.  Or... 
>> Something else :-/. Maybe a lock?  V8 errors are very much a "you screwed 
>> up somewhere" notification and often nothing more 
>>
>> On Tue, Sep 5, 2017 at 9:42 AM Francisco Moraes  
>> wrote:
>>
>>> I will give it a try sometime this week. I tried to remove our 
>>> initialization JS file but that caused a failure further down the 
>>> serialization as well, so still investigating.
>>>
>>>
>>> On Saturday, September 2, 2017 at 1:07:28 AM UTC-4, Zac Hansen wrote:

 Can you post a minimal complete example that reproduces your problem?

 On Friday, September 1, 2017 at 8:57:51 AM UTC-7, Francisco Moraes 
 wrote:
>
> Hello,
>
> I am trying to create a snapshot that includes most of code but I ran 
> into the following assertion:
>
>   CHECK(isolate->handle_scope_implementer()->blocks()->is_empty());
>
> Any clarifications about what would generate it that our JS code is 
> doing and is not legal? I found that creating Unsafe Arrays is also not 
> permitted but that is relatively easy to work around.
>
> Francisco
>
 -- 
>>> -- 
>>> v8-users mailing list
>>> v8-u...@googlegroups.com
>>> http://groups.google.com/group/v8-users
>>> --- 
>>> You received this message because you are subscribed to a topic in the 
>>> Google Groups "v8-users" group.
>>> To unsubscribe from this topic, visit 
>>> https://groups.google.com/d/topic/v8-users/kxtnaSSQL9c/unsubscribe.
>>> To unsubscribe from this group and all its topics, send an email to 
>>> v8-users+u...@googlegroups.com.
>>> For more options, visit https://groups.google.com/d/optout.
>>>
>>
> On Tuesday, September 5, 2017 at 2:50:36 PM UTC-4, Zac Hansen wrote:
>>
>> That kind of error usually means you either haven't created a context or 
>> aren't in a context or haven't created an appropriate handle.  Or... 
>> Something else :-/. Maybe a lock?  V8 errors are very much a "you screwed 
>> up somewhere" notification and often nothing more 
>>
>> On Tue, Sep 5, 2017 at 9:42 AM Francisco Moraes  
>> wrote:
>>
>>> I will give it a try sometime this week. I tried to remove our 
>>> initialization JS file but that caused a failure further down the 
>>> serialization as well, so still investigating.
>>>
>>>
>>> On Saturday, September 2, 2017 at 1:07:28 AM UTC-4, Zac Hansen wrote:

 Can you post a minimal complete example that reproduces your problem?

 On Friday, September 1, 2017 at 8:57:51 AM UTC-7, Francisco Moraes 
 wrote:
>
> Hello,
>
> I am trying to create a snapshot that includes most of code but I ran 
> into the following assertion:
>
>   CHECK(isolate->handle_scope_implementer()->blocks()->is_empty());
>
> Any clarifications about what would generate it that our JS code is 
> doing and is not legal? 

Re: [v8-users] Re: V8 snapshots

[Francisco Moraes]

Here's a simple recreate that I managed to create:

#include 

#include "v8.h"
#include "libplatform/libplatform.h"

int main(int argv, char **argc)
{
const char *v8flags = "";
v8::Platform *platform = v8::platform::CreateDefaultPlatform();
v8::V8::SetFlagsFromString (v8flags, strlen (v8flags));
v8::V8::InitializePlatform(platform);
v8::V8::Initialize();

v8::SnapshotCreator creator;
v8::Isolate *isolate = creator.GetIsolate();

v8::HandleScope handle_scope(isolate);
v8::Local context = v8::Context::New(isolate);
const char* source = "function initialize(obj) { return true; }";
v8::Context::Scope context_scope(context);
v8::TryCatch try_catch(isolate);
v8::Local source_string;
v8::String::NewFromUtf8(isolate, source, v8::NewStringType::kNormal)
.ToLocal(_string);
v8::ScriptOrigin origin = 
v8::ScriptOrigin(v8::String::NewFromUtf8(isolate, "testscript"));
v8::ScriptCompiler::Source sourcecode(source_string, origin);
v8::Local script;
bool success = v8::ScriptCompiler::Compile(context, 
).ToLocal();

script->Run(context);
  
creator.SetDefaultContext(context);
v8::StartupData blob = 
creator.CreateBlob(v8::SnapshotCreator::FunctionCodeHandling::kClear);

return 1;
}

The interesting thing is if I call v8::V8::CreateSnapshotDataBlob it works 
as it does all the above work for me, so something in trying to use the 
SnapshotCreator is causing me some issue as I will need to handle custom 
embedder fields, etc...

On Tuesday, September 5, 2017 at 2:50:36 PM UTC-4, Zac Hansen wrote:
>
> That kind of error usually means you either haven't created a context or 
> aren't in a context or haven't created an appropriate handle.  Or... 
> Something else :-/. Maybe a lock?  V8 errors are very much a "you screwed 
> up somewhere" notification and often nothing more 
>
> On Tue, Sep 5, 2017 at 9:42 AM Francisco Moraes  > wrote:
>
>> I will give it a try sometime this week. I tried to remove our 
>> initialization JS file but that caused a failure further down the 
>> serialization as well, so still investigating.
>>
>>
>> On Saturday, September 2, 2017 at 1:07:28 AM UTC-4, Zac Hansen wrote:
>>>
>>> Can you post a minimal complete example that reproduces your problem?
>>>
>>> On Friday, September 1, 2017 at 8:57:51 AM UTC-7, Francisco Moraes wrote:

 Hello,

 I am trying to create a snapshot that includes most of code but I ran 
 into the following assertion:

   CHECK(isolate->handle_scope_implementer()->blocks()->is_empty());

 Any clarifications about what would generate it that our JS code is 
 doing and is not legal? I found that creating Unsafe Arrays is also not 
 permitted but that is relatively easy to work around.

 Francisco

>>> -- 
>> -- 
>> v8-users mailing list
>> v8-u...@googlegroups.com 
>> http://groups.google.com/group/v8-users
>> --- 
>> You received this message because you are subscribed to a topic in the 
>> Google Groups "v8-users" group.
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>> https://groups.google.com/d/topic/v8-users/kxtnaSSQL9c/unsubscribe.
>> To unsubscribe from this group and all its topics, send an email to 
>> v8-users+u...@googlegroups.com .
>> For more options, visit https://groups.google.com/d/optout.
>>
>
On Tuesday, September 5, 2017 at 2:50:36 PM UTC-4, Zac Hansen wrote:
>
> That kind of error usually means you either haven't created a context or 
> aren't in a context or haven't created an appropriate handle.  Or... 
> Something else :-/. Maybe a lock?  V8 errors are very much a "you screwed 
> up somewhere" notification and often nothing more 
>
> On Tue, Sep 5, 2017 at 9:42 AM Francisco Moraes  > wrote:
>
>> I will give it a try sometime this week. I tried to remove our 
>> initialization JS file but that caused a failure further down the 
>> serialization as well, so still investigating.
>>
>>
>> On Saturday, September 2, 2017 at 1:07:28 AM UTC-4, Zac Hansen wrote:
>>>
>>> Can you post a minimal complete example that reproduces your problem?
>>>
>>> On Friday, September 1, 2017 at 8:57:51 AM UTC-7, Francisco Moraes wrote:

 Hello,

 I am trying to create a snapshot that includes most of code but I ran 
 into the following assertion:

   CHECK(isolate->handle_scope_implementer()->blocks()->is_empty());

 Any clarifications about what would generate it that our JS code is 
 doing and is not legal? I found that creating Unsafe Arrays is also not 
 permitted but that is relatively easy to work around.

 Francisco

>>> -- 
>> -- 
>> v8-users mailing list
>> v8-u...@googlegroups.com 
>> http://groups.google.com/group/v8-users
>> --- 
>> You received this message because you are subscribed to a topic in the 
>> Google Groups "v8-users" group.
>> To unsubscribe from this topic, visit 
>> 

Re: [v8-users] Re: V8 snapshots

[Zac Hansen]

That kind of error usually means you either haven't created a context or
aren't in a context or haven't created an appropriate handle.  Or...
Something else :-/. Maybe a lock?  V8 errors are very much a "you screwed
up somewhere" notification and often nothing more

On Tue, Sep 5, 2017 at 9:42 AM Francisco Moraes 
wrote:

> I will give it a try sometime this week. I tried to remove our
> initialization JS file but that caused a failure further down the
> serialization as well, so still investigating.
>
>
> On Saturday, September 2, 2017 at 1:07:28 AM UTC-4, Zac Hansen wrote:
>>
>> Can you post a minimal complete example that reproduces your problem?
>>
>> On Friday, September 1, 2017 at 8:57:51 AM UTC-7, Francisco Moraes wrote:
>>>
>>> Hello,
>>>
>>> I am trying to create a snapshot that includes most of code but I ran
>>> into the following assertion:
>>>
>>>   CHECK(isolate->handle_scope_implementer()->blocks()->is_empty());
>>>
>>> Any clarifications about what would generate it that our JS code is
>>> doing and is not legal? I found that creating Unsafe Arrays is also not
>>> permitted but that is relatively easy to work around.
>>>
>>> Francisco
>>>
>> --
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Re: [v8-users] Re: V8 Snapshots Questions and Clarifications

[Jakob Kummerow]

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.
 
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