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    SubjectRe: [PATCH v5 07/10] perf record: implement -z,--compression_level=n option and compression
    On Thu, Mar 07, 2019 at 11:39:46AM +0300, Alexey Budankov wrote:
    >
    > On 05.03.2019 15:25, Jiri Olsa wrote:
    > > On Fri, Mar 01, 2019 at 06:58:32PM +0300, Alexey Budankov wrote:
    > >
    > > SNIP
    > >
    > >>
    > >> /*
    > >> * Increment md->refcount to guard md->data[idx] buffer
    > >> @@ -350,7 +357,7 @@ int perf_mmap__aio_push(struct perf_mmap *md, void *to, int idx,
    > >> md->prev = head;
    > >> perf_mmap__consume(md);
    > >>
    > >> - rc = push(to, &md->aio.cblocks[idx], md->aio.data[idx], size0 + size, *off);
    > >> + rc = push(to, md->aio.data[idx], size0 + size, *off, &md->aio.cblocks[idx]);
    > >> if (!rc) {
    > >> *off += size0 + size;
    > >> } else {
    > >> @@ -556,13 +563,15 @@ int perf_mmap__read_init(struct perf_mmap *map)
    > >> }
    > >>
    > >> int perf_mmap__push(struct perf_mmap *md, void *to,
    > >> - int push(struct perf_mmap *map, void *to, void *buf, size_t size))
    > >> + int push(struct perf_mmap *map, void *to, void *buf, size_t size),
    > >> + perf_mmap__compress_fn_t compress, void *comp_data)
    > >> {
    > >> u64 head = perf_mmap__read_head(md);
    > >> unsigned char *data = md->base + page_size;
    > >> unsigned long size;
    > >> void *buf;
    > >> int rc = 0;
    > >> + size_t mmap_len = perf_mmap__mmap_len(md);
    > >>
    > >> rc = perf_mmap__read_init(md);
    > >> if (rc < 0)
    > >> @@ -574,7 +583,10 @@ int perf_mmap__push(struct perf_mmap *md, void *to,
    > >> buf = &data[md->start & md->mask];
    > >> size = md->mask + 1 - (md->start & md->mask);
    > >> md->start += size;
    > >> -
    > >> + if (compress) {
    > >> + size = compress(comp_data, md->data, mmap_len, buf, size);
    > >> + buf = md->data;
    > >> + }
    > >> if (push(md, to, buf, size) < 0) {
    > >> rc = -1;
    > >> goto out;
    > >
    > > when we discussed the compress callback should be another layer
    > > in perf_mmap__push I was thinking more of the layered/fifo design,
    > > like:
    > >
    > > normaly we call:
    > >
    > > perf_mmap__push(... push = record__pushfn ...)
    > > -> reads mmap data and calls push(data), which translates as:
    > >
    > > record__pushfn(data);
    > > - which stores the data
    > >
    > >
    > > for compressed it'd be:
    > >
    > > perf_mmap__push(... push = compressed_push ...)
    > >
    > > -> reads mmap data and calls push(data), which translates as:
    > >
    > > compressed_push(data)
    > > -> reads data, compresses them and calls, next push callback in line:
    > >
    > > record__pushfn(data)
    > > - which stores the data
    > >
    > >
    > > there'd need to be the logic for compressed_push to
    > > remember the 'next push' function
    >
    > That is suboptimal for AIO. Also compression is an independent operation that
    > could be applied on any of push stages you mean.

    not sure what you mean by suboptimal, but I think
    that it can still happen in subsequent push callback

    >
    > >
    > > but I think this was the original idea behind the
    > > perf_mmap__push -> it gets the data and pushes them for
    > > the next processing.. it should stay as simple as that
    >
    > Agree on keeping simplicity and, at the moment, there is no any push to the next
    > processing in the code so provided implementation fits as for serial as for AIO
    > at the same time sticking to simplicity as much as possibly. If you see something
    > that would fit better please speak up and share.

    I have to insist that perf_mmap__push stays untouched
    and we do other processing in the push callbacks

    jirka

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