Hey all, Yeah, we (Cloudflare Workers runtime folks) worked with Igalia and asked them to implement the IsolateGroups mechanism specifically for pointer compression support and would really have no intention of supporting it without pointer compression. In workers we will create thousands of isolates within a single process and can't afford to be limited by the single pointer compression cage for the entire process. We also want to start making use of the v8 sandbox. We were running a non-supported configuration with pointer compression enabled but otherwise diverging from the supported configuration in a way that was not sustainable and isolate groups allow us to have better alignment there. It *might* be possible to have a variation of isolate groups that works without pointer compression but it's not something that we'd be interested in and not something we'd ask our friends at Igalia to work on.
- James On Thu, Jun 12, 2025 at 7:10 AM Michael Lippautz <[email protected]> wrote: > > > On Thu, Jun 12, 2025 at 3:37 PM ClearScript Developers < > [email protected]> wrote: > >> Greetings! >> >> We've run into a new issue in V8 13.7 (upgrading from 13.5). In a >> multi-isolate application, tearing down one isolate can trigger synchronous >> activity in another – specifically, the posting of ReleasePooledChunksTask. >> >> Evidently, that happens because, by default, both isolates are in the >> same group. Our understanding is that isolate groups are a new feature that >> allows isolates to share certain resources, and that, unfortunately, is a >> problem for us. In our case, isolates must remain... isolated. >> >> Setting up a dedicated group for each isolate appears to be possible, but >> isolate groups require pointer compression, which we'd prefer to disable. >> Even if we enabled it, pointer compression isn't supported on 32-bit >> systems, which we still support. >> >> Can someone shed some light? Why do isolate groups require pointer >> compression? How difficult would it be to remove that restriction? >> >> > At this point V8 only officially supports a configuration with a single > IsolateGroup. > > The concept of IsolateGroup was introduced by other embedders and as you > wrote it's really for sharing a bunch of resources. E.g., read-only space, > page pool, and at this point also a pointer compression cage. You could > imagine an IsolateGroup without pointer compression -- at this point this > is just not implemented. > > For maintenance and security reasons we can't accept any non-trivial > patches for this area at this point as we cannot reliably test other > configurations and ensure that they don't cause security problems down the > line. > > -Michael > > > -- > -- > v8-dev mailing list > [email protected] > http://groups.google.com/group/v8-dev > --- > You received this message because you are subscribed to the Google Groups > "v8-dev" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to [email protected]. > To view this discussion visit > https://groups.google.com/d/msgid/v8-dev/CAH%2BmL5CWjvnpqfYPvv_rdsmH6h-x4mWOtzqDCdPjLA%2BV0c4oQA%40mail.gmail.com > <https://groups.google.com/d/msgid/v8-dev/CAH%2BmL5CWjvnpqfYPvv_rdsmH6h-x4mWOtzqDCdPjLA%2BV0c4oQA%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- -- v8-dev mailing list [email protected] http://groups.google.com/group/v8-dev --- You received this message because you are subscribed to the Google Groups "v8-dev" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion visit https://groups.google.com/d/msgid/v8-dev/CACFvHWnXBZNRsFWwJtuoHnXhf4KHZgtQGYdM5z9XBcQXdWh3pA%40mail.gmail.com.
