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Date: Mon, 25 Mar 2024 14:03:22 -0700 From: Namhyung Kim <namhyung@...nel.org> To: Ian Rogers <irogers@...gle.com> Cc: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...nel.org>, Adrian Hunter <adrian.hunter@...el.com>, James Clark <james.clark@....com>, Athira Rajeev <atrajeev@...ux.vnet.ibm.com>, Colin Ian King <colin.i.king@...il.com>, Ahelenia Ziemiańska <nabijaczleweli@...ijaczleweli.xyz>, Leo Yan <leo.yan@...ux.dev>, Song Liu <song@...nel.org>, Miguel Ojeda <ojeda@...nel.org>, Liam Howlett <liam.howlett@...cle.com>, Ilkka Koskinen <ilkka@...amperecomputing.com>, Ben Gainey <ben.gainey@....com>, K Prateek Nayak <kprateek.nayak@....com>, Kan Liang <kan.liang@...ux.intel.com>, Yanteng Si <siyanteng@...ngson.cn>, Ravi Bangoria <ravi.bangoria@....com>, Sun Haiyong <sunhaiyong@...ngson.cn>, Changbin Du <changbin.du@...wei.com>, Masami Hiramatsu <mhiramat@...nel.org>, zhaimingbing <zhaimingbing@...s.chinamobile.com>, Paran Lee <p4ranlee@...il.com>, Li Dong <lidong@...o.com>, elfring@...rs.sourceforge.net, Andi Kleen <ak@...ux.intel.com>, Markus Elfring <Markus.Elfring@....de>, Chengen Du <chengen.du@...onical.com>, linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org, bpf@...r.kernel.org Subject: Re: [PATCH v2 00/13] dso/dsos memory savings and clean up Hi Ian, On Thu, Mar 21, 2024 at 9:03 AM Ian Rogers <irogers@...gle.com> wrote: > > 13 more patches from: > https://lore.kernel.org/lkml/20240202061532.1939474-1-irogers@google.com/ > a near half year old adventure in trying to lower perf's dynamic > memory use. Bits like the memory overhead of opendir are on the > sidelines for now, too much fighting over how > distributions/C-libraries present getdents. These changes are more > good old fashioned replace an rb-tree with a sorted array and add > reference count tracking. > > The changes migrate dsos code, the collection of dso structs, more > into the dsos.c/dsos.h files. As with maps and threads, this is done > so the internals can be changed - replacing a linked list (for fast > iteration) and an rb-tree (for fast finds) with a lazily sorted > array. The complexity of operations remain roughly the same, although > iterating an array is likely faster than iterating a linked list, the > memory usage is at least reduce by half. > > As fixing the memory usage necessitates changing operations like find, > modify these operations so that they increment the reference count to > avoid races like a find in dsos and a remove. Similarly tighten up > lock usage so that operations working on dsos state hold the > appropriate lock. > > Here are some questions (with answers) that I am expecting from reviewers: > > - Why not refactor dso with accessors first and then do the other things? > > My ambition with this change was to lower memory overhead not to > particularly clean up and fix dso. Fixing the memory overhead, by > refactoring and changing the internals, showed that locking discipline > and reference counting discipline was lacking. The later changes try > to fix these as a service to the community while I am changing the > code and to also ensure that code is correct (more correct than it was > wrt locking and reference counting than before the patches). > > Reordering the patches to do the refactoring first will be a giant > pain. It will merge conflict with every other patch in the series and > is basically a request to reimplement everything from square 1. The > only thing I'd have in my favor would be how the code should look at > the end of the series, and reordering patches doesn't change the > eventual outcome of applying the patches. Note also, were I to send > the memory saving patches and then a week later send the API clean up > and reference counting fix patches the patches would be merged in the > order they are here. I've done my best, I know you may consider that > I'm adding to your reviewing overhead but I've also got to think about > the overhead to me. > > - Please break apart this change... > > The first changes are moving things, but when a broken API is spotted > like the missing get on dsos__find I put it in a change to move the > function and to add the missed get. Could this be two changes? Yes, it > could. Does moving code materially change the behavior of the tool? > No. I've done it in one patch to minimize churn and to some extent for > my sanity. Such changes are less than 100 lines of code and all > independently tested. > > - The logic in dso around short, long name and id with sorting is weird > > Yes, I've tried to make it less weird while retaining the existing > behavior. It would be easy to make a series of patches just cleaning > it up but I came here to save memory not change the dso API. > > - Move the fixes in the 12th patch earlier. > > This is possible but then impossible to test with reference count > checking. This does mean there are broken reference counts before the > patch is applied, but this is generally already the case. Yes, some > hypothetical person may decide to fork midway through this patch > series and my order would mean they wouldn't have a fix. I've done my > best while working within the bounds of my time and trying to avoid > churn. > > v2. Rebases on top of tmp.perf-tools-next resolving merge conflicts. > > Ian Rogers (13): > perf dso: Reorder variables to save space in struct dso > perf dsos: Attempt to better abstract dsos internals > perf dsos: Tidy reference counting and locking > perf dsos: Add dsos__for_each_dso > perf dso: Move dso functions out of dsos > perf dsos: Switch more loops to dsos__for_each_dso > perf dsos: Switch backing storage to array from rbtree/list > perf dsos: Remove __dsos__addnew > perf dsos: Remove __dsos__findnew_link_by_longname_id > perf dsos: Switch hand code to bsearch > perf dso: Add reference count checking and accessor functions > perf dso: Reference counting related fixes > perf dso: Use container_of to avoid a pointer in dso_data Acked-by: Namhyung Kim <namhyung@...nel.org> Thanks, Namhyung > > tools/perf/builtin-annotate.c | 8 +- > tools/perf/builtin-buildid-cache.c | 2 +- > tools/perf/builtin-buildid-list.c | 18 +- > tools/perf/builtin-inject.c | 96 +-- > tools/perf/builtin-kallsyms.c | 2 +- > tools/perf/builtin-mem.c | 4 +- > tools/perf/builtin-record.c | 2 +- > tools/perf/builtin-report.c | 6 +- > tools/perf/builtin-script.c | 8 +- > tools/perf/builtin-top.c | 4 +- > tools/perf/builtin-trace.c | 2 +- > tools/perf/tests/code-reading.c | 8 +- > tools/perf/tests/dso-data.c | 67 ++- > tools/perf/tests/hists_common.c | 6 +- > tools/perf/tests/hists_cumulate.c | 4 +- > tools/perf/tests/hists_output.c | 2 +- > tools/perf/tests/maps.c | 4 +- > tools/perf/tests/symbols.c | 8 +- > tools/perf/tests/vmlinux-kallsyms.c | 6 +- > tools/perf/ui/browsers/annotate.c | 6 +- > tools/perf/ui/browsers/hists.c | 8 +- > tools/perf/ui/browsers/map.c | 4 +- > tools/perf/util/annotate-data.c | 14 +- > tools/perf/util/annotate.c | 47 +- > tools/perf/util/auxtrace.c | 2 +- > tools/perf/util/block-info.c | 2 +- > tools/perf/util/bpf-event.c | 8 +- > tools/perf/util/build-id.c | 136 ++--- > tools/perf/util/build-id.h | 2 - > tools/perf/util/callchain.c | 2 +- > tools/perf/util/data-convert-json.c | 2 +- > tools/perf/util/db-export.c | 6 +- > tools/perf/util/dlfilter.c | 12 +- > tools/perf/util/dso.c | 472 +++++++++------ > tools/perf/util/dso.h | 554 +++++++++++++++--- > tools/perf/util/dsos.c | 529 +++++++++++------ > tools/perf/util/dsos.h | 40 +- > tools/perf/util/event.c | 8 +- > tools/perf/util/header.c | 8 +- > tools/perf/util/hist.c | 4 +- > tools/perf/util/intel-pt.c | 22 +- > tools/perf/util/machine.c | 192 ++---- > tools/perf/util/machine.h | 2 + > tools/perf/util/map.c | 82 ++- > tools/perf/util/maps.c | 14 +- > tools/perf/util/probe-event.c | 25 +- > .../util/scripting-engines/trace-event-perl.c | 6 +- > .../scripting-engines/trace-event-python.c | 21 +- > tools/perf/util/session.c | 21 + > tools/perf/util/session.h | 2 + > tools/perf/util/sort.c | 19 +- > tools/perf/util/srcline.c | 65 +- > tools/perf/util/symbol-elf.c | 145 +++-- > tools/perf/util/symbol-minimal.c | 4 +- > tools/perf/util/symbol.c | 186 +++--- > tools/perf/util/symbol_fprintf.c | 4 +- > tools/perf/util/synthetic-events.c | 24 +- > tools/perf/util/thread.c | 4 +- > tools/perf/util/unwind-libunwind-local.c | 18 +- > tools/perf/util/unwind-libunwind.c | 2 +- > tools/perf/util/vdso.c | 56 +- > 61 files changed, 1817 insertions(+), 1220 deletions(-) > > -- > 2.44.0.396.g6e790dbe36-goog >
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