Re: Dynamic shared memory areas

On Wed, Oct 5, 2016 at 3:00 AM, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> Here's a new version that does that.

While testing this patch I found some issue,

+ total_size = DSA_INITIAL_SEGMENT_SIZE;
+ total_pages = total_size / FPM_PAGE_SIZE;
+ metadata_bytes =
+ MAXALIGN(sizeof(dsa_area_control)) +
+ MAXALIGN(sizeof(FreePageManager)) +
+ total_pages * sizeof(dsa_pointer);
+ /* Add padding up to next page boundary. */
+ if (metadata_bytes % FPM_PAGE_SIZE != 0)
+ metadata_bytes += FPM_PAGE_SIZE - (metadata_bytes % FPM_PAGE_SIZE);
+ usable_pages =
+ (total_size - metadata_bytes) / FPM_PAGE_SIZE;

+ segment = dsm_create(total_size, 0);
+ dsm_pin_segment(segment);

Actually problem is that size of dsa_area_control is bigger than
DSA_INITIAL_SEGMENT_SIZE.
but we are allocating segment of DSA_INITIAL_SEGMENT_SIZE size.

(gdb) p sizeof(dsa_area_control)
$8 = 67111000
(gdb) p DSA_INITIAL_SEGMENT_SIZE
$9 = 1048576

In dsa-v1 problem was not exist because DSA_MAX_SEGMENTS was 1024,
but in dsa-v2 I think it's calculated wrongly.

(gdb) p DSA_MAX_SEGMENTS
$10 = 16777216

--
Regards,
Dilip Kumar
EnterpriseDB: http://www.enterprisedb.com