Hi Stephen, On Tue, Aug 4, 2026 at 4:14 AM Stephen Brennan <[email protected]> wrote: > > Hello all, > > Just a gentle ping on this series.
Sorry I was busy recently due to some internal team issues. Anyway I will review the patchset, it's on my queue. Thanks, Tao Liu > > Thanks, > Stephen > > Stephen Brennan <[email protected]> writes: > > Hello all, > > > > Building on Tao Liu's excellent work for makedumpfile extensions, I'd like > > to > > share some incremental improvements to the extension system, as well as my > > own > > two extensions which enable userspace stack tracing. There are three topics > > related to the core makedumpfile extension system which are addressed here: > > > > 1. Tail pages handling. As patch 1 explains, extensions currently get > > called for > > tail pages, but their decisions are not respected. I believe the best > > approach > > is to only call extensions for the head page, but allow extensions to > > return a > > decision related to just a subset of the pages. To this end, patch 7 adds > > PG_INCLUDE_HEAD to include just the head page (leaving the rest up to the > > default policy), and patch 9 shows the elfheader extension which uses that > > functionality. > > > > 2. Counting pages included by extensions. This is done by patch 4. It > > alters the > > logic because it's really helpful to know whether a page would have been > > included by makedumpfile's dump-level filtering anyway, so we only count the > > additional pages. > > > > 3. Sharing makedumpfile's logic and knowledge about page metadata. > > Currently, > > extensions just get a "pcache" pointer, which means they must redo whatever > > logic makedumpfile has already done, in order to get information like > > compound_order. Patches 3, 5, and 6 factor out the page metadata into a new > > struct pginfo, which gets passed to extensions, and it also makes more of > > the > > helpers like "isSlab()" usable with this pointer. > > > > With those improvements, the final two patches (8 & 9) implement a pair of > > extensions that are useful for including a minimal amount of information > > which > > can be used to do stack traces of the userspace processes in a vmcore. The > > "userstack" extension includes the stack memory itself for each thread, and > > the > > "elfheader" extension includes the first page of mapped ELF files, so that > > ELF > > build IDs can be identified from the vmcore. > > > > My testing so far: > > - Live testing (/proc/kcore) x86_64 on Oracle UEK 8 (6.12.x based) > > - Refiltering on vmcores generated from UEK8, 7 (5.15.x based), 6 (5.4.x > > based) > > - Using the resulting filtered vmcores with drgn's contrib/pstack.py to > > generate > > userspace stack traces. > > > > I still have significantly more testing to do and then share out: > > - Testing in kexec environment > > - Testing with upstream kernels, also verifying in a Fedora userspace > > - Sharing runtime and size comparisons with different workloads > > > > Despite the limited testing, I wanted to share these patches as they are, > > because I think the improvements for the core extensions framework are > > useful > > already, and don't require as much verification. > > > > For the extensions themselves, I would like to consider merging them as > > well, if > > there is interest. I think it would be useful for makedumpfile to contain > > shared > > extensions, including those for the GPU buffers which Tao Liu was working > > on, as > > well as the userspace stack tracing ones which I'm sharing. > > > > Thanks, > > Stephen > > > > Stephen Brennan (9): > > Do not call extensions for tail pages > > Honor CFLAGS in extension/Makefile > > Share page information with extension callbacks > > Introduce a stat for pages retained by extension > > Move page checks into makedumpfile.h > > Simplify arguments for page checks > > Add PG_INCLUDE_HEAD extension return status > > Add userstack extension > > Add elfheader extension > > > > extension.c | 10 +- > > extension.h | 10 +- > > extensions/Makefile | 8 +- > > extensions/elfheader.c | 93 ++++++++++++ > > extensions/userstack.c | 325 ++++++++++++++++++++++++++++++++++++++++ > > extensions/vma_mtree.c | 140 +++++++++++++++++ > > extensions/vma_mtree.h | 7 + > > extensions/vma_rbtree.c | 56 +++++++ > > extensions/vma_rbtree.h | 12 ++ > > makedumpfile.c | 188 +++++++++-------------- > > makedumpfile.h | 78 +++++++++- > > 11 files changed, 798 insertions(+), 129 deletions(-) > > create mode 100644 extensions/elfheader.c > > create mode 100644 extensions/userstack.c > > create mode 100644 extensions/vma_mtree.c > > create mode 100644 extensions/vma_mtree.h > > create mode 100644 extensions/vma_rbtree.c > > create mode 100644 extensions/vma_rbtree.h > > > > -- > > 2.47.3 >
