Re: [PATCH v9 1/3]: perf util: map data buffer for preserving collected data

[Namhyung Kim <namhyung@kernel.org>]

On Wed, Oct 03, 2018 at 07:01:26PM +0300, Alexey Budankov wrote:
> 
> The map->data buffer is used to preserve map->base profiling data 
> for writing to disk. AIO map->cblock is used to queue corresponding 
> map->data buffer for asynchronous writing.
> 
> Signed-off-by: Alexey Budankov <alexey.budankov@linux.intel.com>
> ---
> Changes in v9:
>   - implemented NO_AIO and HAVE_AIO_SUPPORT defines to cover cases of 
>     libc implementations without Posix AIO API support
> Changes in v7:
>   - implemented handling record.aio setting from perfconfig file
>  Changes in v6:
>   - adjusted setting of priorities for cblocks;
>  Changes in v5:
>   - reshaped layout of data structures;
>   - implemented --aio option;
>  Changes in v4:
>   - converted mmap()/munmap() to malloc()/free() for mmap->data buffer management 
>  Changes in v2:
>   - converted zalloc() to calloc() for allocation of mmap_aio array,
>   - cleared typo and adjusted fallback branch code;
> ---
>  tools/perf/Makefile.config |  5 +++++
>  tools/perf/Makefile.perf   |  7 ++++++-
>  tools/perf/util/evlist.c   |  4 +++-
>  tools/perf/util/mmap.c     | 31 +++++++++++++++++++++++++++++++
>  tools/perf/util/mmap.h     | 11 +++++++++++
>  5 files changed, 56 insertions(+), 2 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index f6d1a03c7523..2e90f4ce9214 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -355,6 +355,11 @@ endif # NO_LIBELF
>  
>  ifeq ($(feature-glibc), 1)
>    CFLAGS += -DHAVE_GLIBC_SUPPORT
> +  ifndef NO_AIO
> +    ifndef BIONIC
> +        CFLAGS += -DHAVE_AIO_SUPPORT
> +    endif
> +  endif
>  endif
>  
>  ifdef NO_DWARF
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index 92514fb3689f..7becc6a72cf2 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -97,8 +97,13 @@ include ../scripts/utilities.mak
>  # Define LIBCLANGLLVM if you DO want builtin clang and llvm support.
>  # When selected, pass LLVM_CONFIG=/path/to/llvm-config to `make' if
>  # llvm-config is not in $PATH.
> -
> +#
>  # Define NO_CORESIGHT if you do not want support for CoreSight trace decoding.
> +#
> +# Define NO_AIO if you do not want support of Posix AIO based trace
> +# streaming for record mode. Currently Posix AIO trace streaming is
> +# supported only when linking with glibc.
> +#
>  
>  # As per kernel Makefile, avoid funny character set dependencies
>  unexport LC_ALL
> diff --git a/tools/perf/util/evlist.c b/tools/perf/util/evlist.c
> index be440df29615..af2f8c965d7a 100644
> --- a/tools/perf/util/evlist.c
> +++ b/tools/perf/util/evlist.c
> @@ -1029,7 +1029,9 @@ int perf_evlist__mmap_ex(struct perf_evlist *evlist, unsigned int pages,
>  	 * So &mp should not be passed through const pointer.
>  	 */
>  	struct mmap_params mp;
> -
> +#ifdef HAVE_AIO_SUPPORT
> +	mp.nr_cblocks = 0;
> +#endif
>  	if (!evlist->mmap)
>  		evlist->mmap = perf_evlist__alloc_mmap(evlist, false);
>  	if (!evlist->mmap)
> diff --git a/tools/perf/util/mmap.c b/tools/perf/util/mmap.c
> index cdb95b3a1213..5b3727b0c7c0 100644
> --- a/tools/perf/util/mmap.c
> +++ b/tools/perf/util/mmap.c
> @@ -155,6 +155,10 @@ void __weak auxtrace_mmap_params__set_idx(struct auxtrace_mmap_params *mp __mayb
>  
>  void perf_mmap__munmap(struct perf_mmap *map)
>  {
> +#ifdef HAVE_AIO_SUPPORT
> +	if (map->data)
> +		zfree(&map->data);
> +#endif
>  	if (map->base != NULL) {
>  		munmap(map->base, perf_mmap__mmap_len(map));
>  		map->base = NULL;
> @@ -166,6 +170,9 @@ void perf_mmap__munmap(struct perf_mmap *map)
>  
>  int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int cpu)
>  {
> +#ifdef HAVE_AIO_SUPPORT
> +	int delta_max;
> +#endif
>  	/*
>  	 * The last one will be done at perf_mmap__consume(), so that we
>  	 * make sure we don't prevent tools from consuming every last event in
> @@ -190,6 +197,30 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int c
>  		map->base = NULL;
>  		return -1;
>  	}
> +#ifdef HAVE_AIO_SUPPORT
> +	map->nr_cblocks = mp->nr_cblocks;
> +	if (map->nr_cblocks) {
> +		map->data = malloc(perf_mmap__mmap_len(map));
> +		if (!map->data) {
> +			pr_debug2("failed to allocate data buffer, error %d\n",
> +					errno);

I guess the error code is not very useful than the message.  But in
this case it's probably ENOMEM so we can simply omit it.


> +			return -1;
> +		}
> +		/*
> +		 * Use cblock.aio_fildes value different from -1
> +		 * to denote started aio write operation on the
> +		 * cblock so it requires explicit record__aio_sync()
> +		 * call prior the cblock may be reused again.
> +		 */
> +		map->cblock.aio_fildes = -1;
> +		/*
> +		 * Allocate cblock with max priority delta to
> +		 * have faster aio write system calls.
> +		 */
> +		delta_max = sysconf(_SC_AIO_PRIO_DELTA_MAX);
> +		map->cblock.aio_reqprio = delta_max;
> +	}
> +#endif

What about separating this part into a function with the #ifdef.
Providing a dummy function when not defined would make the code
cleaner IMHO.  You may consider adding util/aio.[ch].

Thanks,
Namhyung


>  	map->fd = fd;
>  	map->cpu = cpu;
>  
> diff --git a/tools/perf/util/mmap.h b/tools/perf/util/mmap.h
> index e603314dc792..1b63b6cc7cf9 100644
> --- a/tools/perf/util/mmap.h
> +++ b/tools/perf/util/mmap.h
> @@ -6,6 +6,9 @@
>  #include <linux/types.h>
>  #include <asm/barrier.h>
>  #include <stdbool.h>
> +#ifdef HAVE_AIO_SUPPORT
> +#include <aio.h>
> +#endif
>  #include "auxtrace.h"
>  #include "event.h"
>  
> @@ -26,6 +29,11 @@ struct perf_mmap {
>  	bool		 overwrite;
>  	struct auxtrace_mmap auxtrace_mmap;
>  	char		 event_copy[PERF_SAMPLE_MAX_SIZE] __aligned(8);
> +#ifdef HAVE_AIO_SUPPORT
> +	void 		 *data;
> +	struct aiocb	 cblock;
> +	int		 nr_cblocks;
> +#endif
>  };
>  
>  /*
> @@ -59,6 +67,9 @@ enum bkw_mmap_state {
>  struct mmap_params {
>  	int			    prot, mask;
>  	struct auxtrace_mmap_params auxtrace_mp;
> +#ifdef HAVE_AIO_SUPPORT
> +	int			    nr_cblocks;
> +#endif
>  };
>  
>  int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd, int cpu);