Re: refactoring basebackup.c

Hi,

Did some performance testing by varying TAR_SEND_SIZE with Robert's
refactor patch and without the patch to check the impact.

Below are the details:

*Backup type*: local backup using pg_basebackup
*Data size*: Around 200GB (200 tables - each table around 1.05 GB)
*different TAR_SEND_SIZE values*: 8kb, 32kb (default value), 128kB, 1MB (
1024kB)

*Server details:*
RAM: 500 GB CPU details: Architecture: x86_64 CPU op-mode(s): 32-bit,
64-bit Byte Order: Little Endian CPU(s): 128 Filesystem: ext4

8kb 32kb (default value) 128kB 1024kB
Without refactor patch real 10m22.718s
user 1m23.629s
sys 8m51.410s real 8m36.245s
user 1m8.471s
sys 7m21.520s real 6m54.299s
user 0m55.690s
sys 5m46.502s real 18m3.511s
user 1m38.197s
sys 9m36.517s
With refactor patch (Robert's patch) real 10m11.350s
user 1m25.038s
sys 8m39.226s real 8m56.226s
user 1m9.774s
sys 7m41.032s real 7m26.678s
user 0m54.833s
sys 6m20.057s real 18m17.230s
user 1m42.749s
sys 9m53.704s

The above numbers are taken from the minimum of two runs of each scenario.

I can see, when we have TAR_SEND_SIZE as 32kb or 128kb, it is giving us a
good performance whereas, for 1Mb it is taking 2.5x more time.

Please let me know your thoughts/suggestions on the same.

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Thanks & Regards,
Suraj kharage,
EnterpriseDB Corporation,
The Postgres Database Company.