| From: | Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, John Gorman <johngorman2(at)gmail(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Parallel Seq Scan |
| Date: | 2015-01-28 15:29:52 |
| Message-ID: | CAA4eK1+ACaW3=J4yYuhYfHqrm0MHWmR6hxQV09vn6thoekx0bw@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Wed, Jan 28, 2015 at 7:46 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>
>
> All that aside, I still can't account for the numbers you are seeing.
> When I run with your patch and what I think is your test case, I get
> different (slower) numbers. And even if we've got 6 drives cranking
> along at 400MB/s each, that's still only 2.4 GB/s, not >6 GB/s. So
> I'm still perplexed.
>
I have tried the tests again and found that I have forgotten to increase
max_worker_processes due to which the data is so different. Basically
at higher client count it is just scanning lesser number of blocks in
fixed chunk approach. So today I again tried with changing
max_worker_processes and found that there is not much difference in
performance at higher client count. I will take some more data for
both block_by_block and fixed_chunk approach and repost the data.
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com
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