Re: [PATCH v7 1/2]: perf util: map data buffer for preserving collected data

From: Alexey Budankov
Date: Thu Sep 06 2018 - 07:55:02 EST




On 06.09.2018 14:04, Jiri Olsa wrote:
> On Wed, Sep 05, 2018 at 10:19:56AM +0300, Alexey Budankov wrote:
>
> SNIP
>
>> @@ -166,6 +174,7 @@ void perf_mmap__munmap(struct perf_mmap *map)
>>
>> int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
>> {
>> + int i;
>> /*
>> * 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 +199,50 @@ int perf_mmap__mmap(struct perf_mmap *map, struct mmap_params *mp, int fd)
>> map->base = NULL;
>> return -1;
>> }
>> + map->nr_cblocks = mp->nr_cblocks;
>> + map->cblocks = calloc(map->nr_cblocks, sizeof(struct aiocb*));
>> + if (!map->cblocks) {
>> + pr_debug2("failed to allocate perf event data buffers, error %d\n",
>> + errno);
>> + return -1;
>> + }
>> + map->data = calloc(map->nr_cblocks, sizeof(void*));
>> + if (map->data) {
>> + int delta_max = sysconf(_SC_AIO_PRIO_DELTA_MAX);
>> + for (i = 0; i < map->nr_cblocks; ++i) {
>> + map->data[i] = malloc(perf_mmap__mmap_len(map));
>> + if (map->data[i]) {
>> + int prio;
>> + unsigned char *data = map->data[i];
>> + map->cblocks[i] = (struct aiocb *)&data[map->mask + 1];
>
> the 'struct aiocb' is allocated at the last page of the buffer?
> is that enough space? could we please make this more transparent
> and allocate that space separately?

Would the array of pointers followed by the array of referenced objects fit?

>
> thanks,
> jirka
>