Messages in this thread | | | Date | Fri, 5 Oct 2018 17:48:54 +0900 | From | Namhyung Kim <> | Subject | Re: [PATCH v9 2/3]: perf record: enable asynchronous trace writing |
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On Fri, Oct 05, 2018 at 11:31:11AM +0300, Alexey Budankov wrote: > Hi,
Hi,
> > On 05.10.2018 10:16, Namhyung Kim wrote: > > On Wed, Oct 03, 2018 at 07:12:10PM +0300, Alexey Budankov wrote: > <SNIP> > >> +static void record__aio_sync(struct perf_mmap *md) > >> +{ > >> + struct aiocb *cblock = &md->cblock; > >> + struct timespec timeout = { 0, 1000 * 1000 * 1 }; // 1ms > >> + > >> + do { > >> + if (cblock->aio_fildes == -1 || record__aio_complete(md, cblock)) > >> + return; > >> + > >> + while (aio_suspend((const struct aiocb**)&cblock, 1, &timeout)) { > >> + if (!(errno == EAGAIN || errno == EINTR)) > >> + pr_err("failed to sync perf data, error: %m\n"); > > > > Is there somthing we can do in this error case? Any chance it gets > > stuck in the loop? > > Not really. Currently, in glibc, it can block on a mutex only.
OK, I was thinking of a situation where the aio_suspend() keeps returning a same error code repeated..
> > > > > > >> + } > >> + } while (1); > >> +} > >> + > >> +static int record__aio_pushfn(void *to, struct aiocb *cblock, void *bf, size_t size) > >> +{ > >> + off_t off; > >> + struct record *rec = to; > >> + int ret, trace_fd = rec->session->data->file.fd; > >> + > >> + rec->samples++; > >> + > >> + off = lseek(trace_fd, 0, SEEK_CUR); > >> + lseek(trace_fd, off + size, SEEK_SET); > > > > It'd be nice if these lseek() could be removed and use > > rec->bytes_written instead. > > Well, this could be implemented like this avoiding lseek() in else branch: > > off = lseek(trace_fd, 0, SEEK_CUR); > ret = record__aio_write(cblock, trace_fd, bf, size, off); > if (!ret) { > lseek(trace_fd, off + size, SEEK_SET); > rec->bytes_written += size; > > if (switch_output_size(rec)) > trigger_hit(&switch_output_trigger); > }
Oh I meant the both like:
off = rec->bytes_written; ret = record__aio_write(cblock, trace_fd, bf, size, off); if (!ret) { rec->bytes_written += size;
...
> > > > > >> + ret = record__aio_write(cblock, trace_fd, bf, size, off); > >> + if (!ret) { > >> + rec->bytes_written += size; > >> + > >> + if (switch_output_size(rec)) > >> + trigger_hit(&switch_output_trigger); > > > > Doesn't it need the _sync() before the trigger? Maybe it should be > > moved to record__mmap_read_evlist() or so.. > > Currently trigger just updates variable state. > The state is then checked thru separate API at __cmd_record() where > record__mmap_read_sync() is called prior switching to a new trace file > or finishing collection. > > >> > <SNIP> > >> if (map->base) { > >> +#ifndef HAVE_AIO_SUPPORT > >> if (perf_mmap__push(map, rec, record__pushfn) != 0) { > >> rc = -1; > >> goto out; > >> } > >> +#else > >> + if (!rec->opts.nr_cblocks) { > >> + if (perf_mmap__push(map, rec, record__pushfn) != 0) { > >> + rc = -1; > >> + goto out; > >> + } > >> + } else { > >> + /* > >> + * Call record__aio_sync() to wait till map->data buffer > >> + * becomes available after previous aio write request. > >> + */ > >> + record__aio_sync(map); > >> + if (perf_mmap__aio_push(map, rec, record__aio_pushfn) != 0) { > >> + rc = -1; > >> + goto out; > >> + } > >> + } > >> +#endif > > > > If dummy aio functions are provided, the #ifdef can be removed and > > just use the #else part assuming opts.nr_cblocks == 0. > > Yes, it looks a little bit cumbersome. Would this be more compact?
Why not exposing opts.nr_cblocks regardless of the #ifdef? It'll have 0 when it's not compiled in. Then it could be like below (assuming you have all the dummy aio funcitons):
> > if (map->base) { > if (!rec->opts.nr_cblocks) { > if (perf_mmap__push(map, rec, record__pushfn) != 0) { > rc = -1; > goto out; > } > } else { > int idx; > /* > * Call record__aio_sync() to wait till map->data buffer > * becomes available after previous aio write request. > */ > idx = record__aio_sync(map, false); > if (perf_mmap__aio_push(map, rec, idx, record__aio_pushfn) != 0) { > rc = -1; > goto out; > } > } > } >
Thanks, Namhyung
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