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SubjectRe: [PATCH v2 2/4] perf record: implement -z=<level> and --mmap-flush=<thres> options
On Mon, Feb 11, 2019 at 11:22:38PM +0300, Alexey Budankov wrote:

SNIP

> static int process_synthesized_event(struct perf_tool *tool,
> union perf_event *event,
> struct perf_sample *sample __maybe_unused,
> @@ -543,7 +574,8 @@ static int record__mmap_evlist(struct record *rec,
> if (perf_evlist__mmap_ex(evlist, opts->mmap_pages,
> opts->auxtrace_mmap_pages,
> opts->auxtrace_snapshot_mode,
> - opts->nr_cblocks, opts->affinity) < 0) {
> + opts->nr_cblocks, opts->affinity,
> + opts->mmap_flush) < 0) {
> if (errno == EPERM) {
> pr_err("Permission error mapping pages.\n"
> "Consider increasing "
> @@ -734,7 +766,7 @@ static void record__adjust_affinity(struct record *rec, struct perf_mmap *map)
> }
>
> static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evlist,
> - bool overwrite)
> + bool overwrite, bool sync)
> {
> u64 bytes_written = rec->bytes_written;
> int i;
> @@ -757,12 +789,19 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
> off = record__aio_get_pos(trace_fd);
>
> for (i = 0; i < evlist->nr_mmaps; i++) {
> + u64 flush = MMAP_FLUSH_DEFAULT;
> struct perf_mmap *map = &maps[i];
>
> if (map->base) {
> record__adjust_affinity(rec, map);
> + if (sync) {
> + flush = map->flush;
> + map->flush = MMAP_FLUSH_DEFAULT;
> + }
> if (!record__aio_enabled(rec)) {
> if (perf_mmap__push(map, rec, record__pushfn) != 0) {
> + if (sync)
> + map->flush = flush;
> rc = -1;
> goto out;
> }
> @@ -775,10 +814,14 @@ static int record__mmap_read_evlist(struct record *rec, struct perf_evlist *evli
> idx = record__aio_sync(map, false);
> if (perf_mmap__aio_push(map, rec, idx, record__aio_pushfn, &off) != 0) {
> record__aio_set_pos(trace_fd, off);
> + if (sync)
> + map->flush = flush;
> rc = -1;
> goto out;
> }
> }
> + if (sync)
> + map->flush = flush;
> }

what's 'flush' and 'sync' for? also the above handling seems confusing,
why would you set it temporarily for default value if you let it set
by user command line option?

SNIP

> -static void perf_mmap__aio_munmap(struct perf_mmap *map __maybe_unused)
> +static void perf_mmap__aio_munmap_blocks(struct perf_mmap *map __maybe_unused)
> {
> }
> #endif
> @@ -444,6 +468,8 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int c
> &mp->auxtrace_mp, map->base, fd))
> return -1;
>
> + map->flush = mp->flush;
> +
> return perf_mmap__aio_mmap(map, mp);
> }
>
> @@ -492,7 +518,7 @@ static int __perf_mmap__read_init(struct perf_mmap *md)
> md->start = md->overwrite ? head : old;
> md->end = md->overwrite ? old : head;
>
> - if (md->start == md->end)
> + if ((md->end - md->start) < md->flush)
> return -EAGAIN;

we need document and explain this change in changelog in separate patch

thanks,
jirka

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