On 05.06.2020 13:50, Jiri Olsa wrote:
> On Wed, Jun 03, 2020 at 06:52:59PM +0300, Alexey Budankov wrote:
>>
>> Implement adding of file descriptors by fdarray__add_stat() to
>> fix-sized (currently 1) stat_entries array located at struct fdarray.
>> Append added file descriptors to the array used by poll() syscall
>> during fdarray__poll() call. Copy poll() result of the added
>> descriptors from the array back to the storage for analysis.
>>
>> Signed-off-by: Alexey Budankov <alexey.budan...@linux.intel.com>
>> ---
>> tools/lib/api/fd/array.c | 42 +++++++++++++++++++++++-
>> tools/lib/api/fd/array.h | 7 ++++
>> tools/lib/perf/evlist.c | 11 +++++++
>> tools/lib/perf/include/internal/evlist.h | 2 ++
>> 4 files changed, 61 insertions(+), 1 deletion(-)
>>
>> diff --git a/tools/lib/api/fd/array.c b/tools/lib/api/fd/array.c
>> index 58d44d5eee31..b0027f2169c7 100644
>> --- a/tools/lib/api/fd/array.c
>> +++ b/tools/lib/api/fd/array.c
>> @@ -11,10 +11,16 @@
>>
>> void fdarray__init(struct fdarray *fda, int nr_autogrow)
>> {
>> + int i;
>> +
>> fda->entries = NULL;
>> fda->priv = NULL;
>> fda->nr = fda->nr_alloc = 0;
>> fda->nr_autogrow = nr_autogrow;
>> +
>> + fda->nr_stat = 0;
>> + for (i = 0; i < FDARRAY__STAT_ENTRIES_MAX; i++)
>> + fda->stat_entries[i].fd = -1;
>> }
>>
>> int fdarray__grow(struct fdarray *fda, int nr)
>> @@ -83,6 +89,20 @@ int fdarray__add(struct fdarray *fda, int fd, short
>> revents)
>> return pos;
>> }
>>
>> +int fdarray__add_stat(struct fdarray *fda, int fd, short revents)
>> +{
>> + int pos = fda->nr_stat;
>> +
>> + if (pos >= FDARRAY__STAT_ENTRIES_MAX)
>> + return -1;
>> +
>> + fda->stat_entries[pos].fd = fd;
>> + fda->stat_entries[pos].events = revents;
>> + fda->nr_stat++;
>> +
>> + return pos;
>> +}
>> +
>> int fdarray__filter(struct fdarray *fda, short revents,
>> void (*entry_destructor)(struct fdarray *fda, int fd, void
>> *arg),
>> void *arg)
>> @@ -113,7 +133,27 @@ int fdarray__filter(struct fdarray *fda, short revents,
>>
>> int fdarray__poll(struct fdarray *fda, int timeout)
>> {
>> - return poll(fda->entries, fda->nr, timeout);
>> + int nr, i, pos, res;
>> +
>> + nr = fda->nr;
>> +
>> + for (i = 0; i < fda->nr_stat; i++) {
>> + if (fda->stat_entries[i].fd != -1) {
>> + pos = fdarray__add(fda, fda->stat_entries[i].fd,
>> + fda->stat_entries[i].events);
>
> so every call to fdarray__poll will add whatever is
> in stat_entries to entries? how is it removed?
Whatever stat fd which is not -1 is added. If static fd is -1 then it is
skipped for
poll() call. Complete stat slot (fd == -1) isn't expected to be reused but
reuse could
be supported by simple change at fdarray__add_stat()
and probably bring required generality.
>
> I think you should either follow what Adrian said
> and put 'static' descriptors early and check for
> filter number to match it as an 'quick fix'
>
> or we should fix it for real and make it generic
It would complicate without a reason. If it really matters I would add
possibility of
realloc of stat entries in fdarray__add_stat() and that would make stat entries
usage
more similar to filterable ones without dramatic change and risk of regressions.
~Alexey
>
> so currently the interface is like this:
>
> pos1 = fdarray__add(a, fd1 ... );
> pos2 = fdarray__add(a, fd2 ... );
> pos3 = fdarray__add(a, fd2 ... );
>
> fdarray__poll(a);
>
> num = fdarray__filter(a, revents, destructor, arg);
>
> when fdarray__filter removes some of the fds the 'pos1,pos2,pos3'
> indexes are not relevant anymore
>
> how about we make the 'pos indexes' being stable by allocating
> separate object for each added descriptor and each poll call
> would create pollfd array from current objects, and entries
> would keep pointer to its pollfd entry
>
> struct fdentry *entry {
> int fd;
> int events;
> struct pollfd *pollfd;
> }
>
> entry1 = fdarray__add(a, fd1 ...);
> entry2 = fdarray__add(a, fd2 ...);
> entry3 = fdarray__add(a, fd3 ...);
>
> fdarray__poll(a);
>
> struct pollfd *fdarray__entry_pollfd(a, entry1);
>
> or smoething like that ;-)
>
> jirka
>
