On Tue, Mar 5, 2024 at 8:50 AM vignesh C <vignes...@gmail.com> wrote: > > On Wed, 28 Feb 2024 at 11:40, Amit Kapila <amit.kapil...@gmail.com> wrote: > > > > On Mon, Feb 26, 2024 at 7:54 PM Masahiko Sawada <sawada.m...@gmail.com> > > wrote: > > > > > > > A few comments on 0003: > > =================== > > 1. > > +/* > > + * Threshold of the total number of top-level and sub transactions > > that controls > > + * whether we switch the memory track state. While the MAINTAIN_HEAP state > > is > > + * effective when there are many transactions being decoded, in many > > systems > > + * there is generally no need to use it as long as all transactions > > being decoded > > + * are top-level transactions. Therefore, we use MaxConnections as > > the threshold > > + * so we can prevent switch to the state unless we use subtransactions. > > + */ > > +#define REORDER_BUFFER_MEM_TRACK_THRESHOLD MaxConnections > > > > The comment seems to imply that MAINTAIN_HEAP is useful for large > > number of transactions but ReorderBufferLargestTXN() switches to this > > state even when there is one transaction. So, basically we use the > > binary_heap technique to get the largest even when we have one > > transaction but we don't maintain that heap unless we have > > REORDER_BUFFER_MEM_TRACK_THRESHOLD number of transactions are > > in-progress. This means there is some additional work when (build and > > reset heap each time when we pick largest xact) we have fewer > > transactions in the system but that may not be impacting us because of > > other costs involved like serializing all the changes. I think once we > > can try to stress test this by setting > > debug_logical_replication_streaming to 'immediate' to see if the new > > mechanism has any overhead. > > I ran the test with a transaction having many inserts: > > | 5000 | 10000 | 20000 | 100000 | 1000000 | 10000000 > ------- > |-----------|------------|------------|--------------|----------------|---------------- > Head | 26.31 | 48.84 | 93.65 | 480.05 | 4808.29 | 47020.16 > Patch | 26.35 | 50.8 | 97.99 | 484.8 | 4856.95 | 48108.89 > > The same test with debug_logical_replication_streaming= 'immediate' > > | 5000 | 10000 | 20000 | 100000 | 1000000 | 10000000 > ------- > |-----------|------------|------------|--------------|----------------|---------------- > Head | 59.29 | 115.84 | 227.21 | 1156.08 | 11367.42 | 113986.14 > Patch | 62.45 | 120.48 | 240.56 | 1185.12 | 11855.37 | 119921.81 > > The execution time is in milliseconds. The column header indicates the > number of inserts in the transaction. > In this case I noticed that the test execution with patch was taking > slightly more time.
I have ran the tests that Vignesh had reported a issue, the test results with the latest patch is given below: Without debug_logical_replication_streaming= 'immediate' Record|10000000 |1000000 |100000 | 20000 | 10000 | 5000 ----------|---------------|-------------|-----------|----------|----------|---------- Head |47563.759| 4917.057|478.923|97.28 |50.368 |25.917 Patch |47445.733| 4722.874|472.817|95.15 |48.801 |26.168 %imp |0.248 | 03.949 |01.274 |02.189|03.111 |-0.968 With debug_logical_replication_streaming= 'immediate' Record| 10000000 | 1000000 | 100000 | 20000 | 10000 | 5000 ----------|----------------|--------------|-------------|-----------|-----------|---------- Head |106281.236|10669.992|1073.815|214.287|107.62 |54.947 Patch |103108.673|10603.139|1064.98 |210.229|106.321|54.218 %imp | 02.985 | 0.626 |0.822 |01.893 |01.207 |01.326 The execution time is in milliseconds. The column header indicates the number of inserts in the transaction. I can notice with the test result that the issue has been resolved with the new patch. Thanks and Regards, Shubham Khanna.
