[webkit-dev] Is there a way to avoid the 16.8 MB RegisterFile memory usage?
mjs at apple.com
Tue Aug 26 02:20:03 PDT 2008
On Aug 26, 2008, at 12:24 AM, Paul Pedriana wrote:
> Thanks for the info about the smaller RegisterFile size; I'll try
> reducing it for myself and see how it goes.
> The RegisterFile.h code has a to-do/fix-me comment for Win32 saying
> to switch from malloc to VirtualAlloc. FWIW, my vote would be to not
> make direct calls to OS memory functions within RegisterFile or
> WebKit in general, at least for non-Unix/Mac builds. Primarily this
> is because it makes assumptions about what the user wants to do or
> what the system can do which might not be true. Doing system level
> memory allocations also prevents the application from measuring
> memory usage and implementing heap validation. At the least, a user-
> overridable allocation function can be used and which defaults to
> using operator new (at least outside Unix variants). This would also
> have the benefit of allowing the code to work across all platforms
> out of the box.
WebKit porters are welcome to choose whatever is appropriate for their
port, taking into account system assumptions. For users of the public
API, I think explicit allocation control would be kind of dodgy.
> On Windows, VirtualAlloc isn't likely to buy much because AFAIK
> VirtualAlloc doesn't have the property whereby it commits pages on
> demand, though it's possible that a future version of Windows may do
It doesn't demand-commit but it does let you separate commit and
reserve, which means you could decommit when exiting JS execution for
> However, in the meantime if the user can implement these allocations
> then it's possible for a user to create a page protected heap that
> works like the Windows process stack and manually commit upon a page
> fault. With that approach you can also manually extend the mapped
> memory beyond the original VirtualAlloc size in case the memory
> requirement becomes huge.
If the memory requirement gets that big there's probably runaway
recursion so we're ok with killing the computation.
>> The RegisterFile is the amount of memory available on the JS stack,
>> reducing it directly reduces the amount of stack, and hence
>> that js code can do. That said, the RegisterFile allocation should
>> result in delayed paging -- eg. it should only be reserving address
>> space, and the OS won't actually allocate memory until we attempt to
>> use it. At least if mmap exists and is usable.
>> On Aug 25, 2008, at 5:25 PM, Cedric Vivier wrote:
>>> On Tue, Aug 26, 2008 at 12:04 AM, Geoffrey Garen <ggaren at apple.com>
>>>> If you want the RegisterFile to be 512K, just change its size to
>>>> that helps.
>>> I am curious as well as Mark, what are the consequences of
>>> (or increasing) this value ? [besides the memory usage of course]
>>> webkit-dev mailing list
>>> webkit-dev at lists.webkit.org
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>> webkit-dev at lists.webkit.org
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