Messages in this thread | | | Date | Fri, 26 Jun 2020 11:37:45 +0200 | From | Jiri Olsa <> | Subject | Re: [PATCH v8 01/13] tools/libperf: avoid moving of fds at fdarray__filter() call |
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On Thu, Jun 25, 2020 at 10:32:29PM +0300, Alexey Budankov wrote: > > 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
I'm confused, are you talking about file descriptors limit now? this wont be affected by epoll change.. what do I miss?
I thought your concern was fs.epoll.max_user_watches, which has default value that seems to be enough:
$ cat /proc/sys/fs/epoll/max_user_watches 3169996
jirka
> > 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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