Messages in this thread | | | Subject | Re: [PATCH v8 01/13] tools/libperf: avoid moving of fds at fdarray__filter() call | From | Alexey Budankov <> | Date | Thu, 25 Jun 2020 22:32:29 +0300 |
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On 25.06.2020 20:14, Jiri Olsa wrote: > On Wed, Jun 24, 2020 at 08:19:32PM +0300, Alexey Budankov wrote: >> >> On 17.06.2020 11:35, Alexey Budankov wrote: >>> >>> Skip fds with zeroed revents field from count and avoid fds moving >>> at fdarray__filter() call so fds indices returned by fdarray__add() >>> call stay the same and can be used for direct access and processing >>> of fd revents status field at entries array of struct fdarray object. >>> >>> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com> >>> --- >>> tools/lib/api/fd/array.c | 11 +++++------ >>> tools/perf/tests/fdarray.c | 20 ++------------------ >>> 2 files changed, 7 insertions(+), 24 deletions(-) >>> >>> diff --git a/tools/lib/api/fd/array.c b/tools/lib/api/fd/array.c >>> index 58d44d5eee31..97843a837370 100644 >>> --- a/tools/lib/api/fd/array.c >>> +++ b/tools/lib/api/fd/array.c >>> @@ -93,22 +93,21 @@ int fdarray__filter(struct fdarray *fda, short revents, >>> return 0; >>> >>> for (fd = 0; fd < fda->nr; ++fd) { >>> + if (!fda->entries[fd].revents) >>> + continue; >>> + >> >> So it looks like this condition also filters out non signaling events fds, not only >> control and others fds, and this should be somehow avoided so such event related fds >> would be counted. Several options have been proposed so far: >> >> 1) Explicit typing of fds via API extension and filtering based on the types: >> a) with separate fdarray__add_stat() call >> b) with type arg of existing fdarray__add() call >> c) various memory management design is possible >> >> 2) Playing tricks with fd positions inside entries and assumptions on fdarray API calls ordering >> - looks more like a hack than a designed solution >> >> 3) Rewrite of fdarray class to allocate separate object for every added fds >> - can be replaced with nonscrewing of fds by __filter() >> >> 4) Distinct between fds types at fdarray__filter() using .revents == 0 condition >> - seems to have corner cases and thus not applicable >> >> 5) Extension of fdarray__poll(, *arg_ptr, arg_size) with arg of fds array to atomically poll >> on fdarray_add()-ed fds and external arg fds and then external arg fds processing >> >> 6) Rewrite of fdarray class on epoll() call basis >> - introduces new scalability restrictions for Perf tool > > hum, how many fds for polling do you expect in your workloads?
Currently it is several hundreds so default of 1K is easily hit and "Profile a Large Number of PMU Events on Multi-Core Systems" section [1] recommends:
soft nofile 65535 hard nofile 65535
for for /etc/security/limits.conf settings.
~Alexey
[1] https://software.intel.com/content/www/us/en/develop/documentation/vtune-cookbook/top/configuration-recipes/profiling-hardware-without-sampling-drivers.html
> > jirka >
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