On 3/06/20 3:52 pm, Alexey Budankov wrote: > > On 03.06.2020 15:30, Hunter, Adrian wrote: >> >> >>> -----Original Message----- >>> From: Hunter, Adrian <[email protected]> >>> Sent: Wednesday, June 3, 2020 3:24 PM >>> To: Alexey Budankov <[email protected]> >>> Cc: Arnaldo Carvalho de Melo <[email protected]>; Jiri Olsa >>> <[email protected]>; Namhyung Kim <[email protected]>; Alexander >>> Shishkin <[email protected]>; Peter Zijlstra >>> <[email protected]>; Ingo Molnar <[email protected]>; Andi Kleen >>> <[email protected]>; linux-kernel <[email protected]> >>> Subject: Re: [PATCH v6 01/13] tools/libperf: introduce notion of static >>> polled >>> file descriptors >>> >>> On 3/06/20 3:01 pm, Alexey Budankov wrote: >>>> Hi, >>>> >>>> On 03.06.2020 14:38, Adrian Hunter wrote: >>>>> On 1/06/20 11:05 pm, 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 separate analysis. >>>>> >>>>> Why not instead call evlist__add_pollfd() before other fds are added, >>>>> so the fda->entries[] position is always fixed. Then this patch is not >>> needed. >>>> >>>> It then will block event consumption loop, at least in record mode, >>>> due to change sin initial assumptions behind fdarray__filter(). So >>>> extension of the API with 'static' fds looks safer w.r.t. possible >>>> functional regressions at the same time extending the API with ability >>>> to atomically wait for (poll()) not only event fds but also any other fds >>> during monitoring. >>> >>> So make fdarray__filter() return the number of filterable fds remaining. >>> >> >> >> Or perhaps simpler, compare the return value to the number of fds that are >> known not to be filterable > > Well, various implementations are for sure possible but the proposed design > avoids implicit code assumptions and dependency on API calls order as in API > implementation as in client code and that is why it's been proposed this way. >
The dependencies are confined one function, namely __cmd_record(), it is simpler, and avoids the inelegant changes to fdarray__poll().
