Re: Dynamic shared memory areas - Mailing list pgsql-hackers

From Dilip Kumar
Subject Re: Dynamic shared memory areas
Date
Msg-id CAFiTN-t9fmNRUsw2+go1rchR90eezcygq6LN-TjsiPiENZEUdQ@mail.gmail.com
Whole thread Raw
In response to Re: Dynamic shared memory areas  (Thomas Munro <thomas.munro@enterprisedb.com>)
Responses Re: Dynamic shared memory areas  (Thomas Munro <thomas.munro@enterprisedb.com>)
List pgsql-hackers
On Wed, Oct 5, 2016 at 3:00 AM, Thomas Munro
<thomas.munro@enterprisedb.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



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