Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

8264543: Cross modify fence optimization for x86 #3334

wants to merge 1 commit into
base: master
Choose a base branch


Copy link

@xbzhang99 xbzhang99 commented Apr 2, 2021

Intel introduced a new instruction “serialize” which ensures that all modifications to flags, registers, and memory by previous instructions are completed and all buffered writes are drained to memory before the next instruction is fetched and executed. It is a serializing instruction and can be used to implement cross modify fence (OrderAccess::cross_modify_fence_impl) more efficiently than using “cpuid” on supported 32-bit and 64-bit x86 platforms.

The availability of the SERIALIZE instruction is indicated by the presence of the CPUID feature flag SERIALIZE, bit 14 of the EDX register in sub-leaf CPUID:7H.0H.


  • Change must not contain extraneous whitespace
  • Commit message must refer to an issue
  • Change must be properly reviewed



Using git

Checkout this PR locally:
$ git fetch pull/3334/head:pull/3334
$ git checkout pull/3334

Update a local copy of the PR:
$ git checkout pull/3334
$ git pull pull/3334/head

Using Skara CLI tools

Checkout this PR locally:
$ git pr checkout 3334

View PR using the GUI difftool:
$ git pr show -t 3334

Using diff file

Download this PR as a diff file:

…modify fence, on supported platforms
Copy link

@bridgekeeper bridgekeeper bot commented Apr 2, 2021

👋 Welcome back xbzhang99! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

@openjdk openjdk bot added the rfr label Apr 2, 2021
Copy link

@openjdk openjdk bot commented Apr 2, 2021

@xbzhang99 The following label will be automatically applied to this pull request:

  • hotspot

When this pull request is ready to be reviewed, an "RFR" email will be sent to the corresponding mailing list. If you would like to change these labels, use the /label pull request command.

@openjdk openjdk bot added the hotspot label Apr 2, 2021
Copy link

@mlbridge mlbridge bot commented Apr 2, 2021


@xbzhang99 xbzhang99 changed the title 8264543: Using Intel serialize instruction to replace cpuid in Cross modify fence, on supported platforms 8264543: Cross modify fence optimization for x86 Apr 5, 2021
Copy link

@gerard-ziemski gerard-ziemski commented Apr 8, 2021

If this is an optimization, do you have any numbers that show an improvement with this change?

Copy link
Contributor Author

@xbzhang99 xbzhang99 commented May 4, 2021

Hi Gerard,
Although we don't have benchmark data yet, serialize is the recommended alternative vs. using CPUID. Also, in the virtual machine environment, serialize provides full/fast serialization without causing VMEXIT

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment
2 participants