Hi Joyee, The heap snapshot indeed uses native memory. The only caveat with taking heap snapshot inside NearHeapLimitCallback is that the callback may be invoked by one of the GCs that are triggered by the heap snapshot generator. So the callback has to be re-entrant (it seems that your PR is already handling this case). If the second callback does not increase the heap limit sufficiently (e.g. max young generation size ~ 32MB by default) then the GC may crash with OOM because it may need to promote young objects into the old generation, which checks the limit.
Other than that it should be safe. Cheers, Ulan. On Thu, Apr 23, 2020 at 1:50 AM Joyee Cheung <jo...@igalia.com> wrote: > I had been thinking that taking heap snapshots should not be viable since > this also consumes memory, but it seems to work just fine when I tried to > implement it in Node.js https://github.com/nodejs/node/pull/33010 - > probably because taking the heap snapshot doesn't really consume that much > memory from the V8 heap, it just mostly uses usual native memory ? > > And the fact that taking heap snapshots triggers GC seem to help > generating multiple snapshots for users to compare, compared to writing > just one when V8 is about to crash which is what > https://github.com/blueconic/node-oom-heapdump does with the OOM > callback. Though thinking about it a bit more, if node-oom-heapdump has > been working, then at least taking heap snapshots is already safe even when > the heap limit is already reached. > > My question is, is this safe? Or to what extent is this safe? > > -- > -- > 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. > To view this discussion on the web visit > https://groups.google.com/d/msgid/v8-users/3bdb87b9-4833-4629-bf98-2ce5a66746cc%40googlegroups.com > <https://groups.google.com/d/msgid/v8-users/3bdb87b9-4833-4629-bf98-2ce5a66746cc%40googlegroups.com?utm_medium=email&utm_source=footer> > . > -- -- 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. To view this discussion on the web visit https://groups.google.com/d/msgid/v8-users/CABNJt2KgQwDV9TXnZSsFS%2BTk0Xzits41DHxHrNOT2bXEC9fSoQ%40mail.gmail.com.
