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Thanks, Stephen Stephen Brennan 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