Pre-fork does not equal to idle connections! Pre-fork
scales with database load where as persistent
connections scales with webserver load. A web server
that is heavily loaded but not necessarily performing
a lot of database activity will spawn hundreds of idle
database connections using persistent connection. With
pre-fork, you can potentially lower this down to even
10 open connections.
Forking is quite fast on Linux but creating a new
process is still 10x more expensive than creating a
thread and is even worse on Win32 platform. CPU load
goes up because the OS needs to allocate/deallocate
memory making it difficult to get a steady state
resource consumption.
More importantly, solving the forking delay will have
a big impact on people's mind who have been given the
impression that forking is very very slow. Here's what
one site has to say about PostgreSQL's forking:
http://www.geocities.com/mailsoftware42/db/
"Postgres forks on every incoming connection - and the
forking process and backend setup is a bit slow, but
one can speed up PostgreSQL by coding things as stored
procedures"
Pre-fork will give MySQL one less argument to throw at
PostgreSQL.
I think optimizing is this area will speed up the
general case for everyone rather than optimizing a
feature that affects 10% of the users. On top of that,
it will make a strong marketing case because forking
will no longer become a speed issue when compared to
MySQL.
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