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

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

jirka

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