Patch to remove excessive fcntl() calls was never ported correctly to 5.1

[Laurynas Biveinis]

This patch -
http://www.percona.com/doc/percona-server/5.1/performance/remove_fcntl_excessive_calls.html
https://bugs.launchpad.net/percona-server/+bug/606810

has always been a no-op in PS 5.1.

The reason is that the patch works by preprocessor, adding "... && !defined(NO_ALARM) " several times to net_serv.cc to disable the alarm code. But nothing in PS build process or official binary build scripts actually define NO_ALARM, it never gets defined, the alarm code never gets disabled.

Not a bug on PS 5.5, as CMake build sys starts defining NO_ALARM for us.

[Alexey Kopytov (akopytov)]

I'm more in favor of keeping the status quo and just fixing the docs to remove the feature, because:

1. Even though the patch was there, the feature was never enabled in our official 5.1 binaries
2. Enabling the feature in our 5.1 binaries would lead to either http://bugs.mysql.com/bug.php?id=52633, or (if the fix is backported) to an unconditional change from the documented behavior in net_read_timeout/net_write_timeout/net_retry_count in upstream 5.1.

Either outcome doesn't look good to me. Let's change it to a doc bug?

[Laurynas Biveinis (laurynas-biveinis)]

Yes, and my MP'ed fix already includes the 52633 backport. Can we document that net_read_timeout and friends behave like on 5.5 instead? IM*H*O it's a relatively low-impact changes that comes close to DTRT.

One more thing backported by this fix is that SIGNAL_WITH_VIO_CLOSE is unconditionally defined, just like on 5.5.

[Alexey Kopytov (akopytov)]

I don't like deviating from a documented 5.1 upstream behavior. There must be a way to move from and to upstream without changes to configuration file (and enabling PS-specific features).

[Alexey Kopytov (akopytov)]

And another argument for keeping the status quo in 5.1 is that it's legacy. I.e. "don't touch unless you absolutely have to".

[Laurynas Biveinis (laurynas-biveinis)]

Right, PS is not a drop-in anymore. Re-assigning to Hrvoje to document the current state.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PS-2813