[MERGE] log performance

[John Arbash Meinel]

Aaron Bentley wrote:
> Robert Widhopf-Fenk wrote:
>>> On Thursday, June 22, 2006 at 22:46:19, Aaron Bentley wrote:
>>> If you have time look at the two messages with
>>>
>>>   Subject: [PATCH] move lock_read() into "bzr log" 
>>>
>>> The extra lock really gives a felt speedup of 2 on remote
>>> repos when getting only a few logs.
> 
> There is no way I would consider removing the lock from show_log.
> cmd_log is not the only caller, and acquiring an already-held lock is
> extremely cheap.
> 
> I don't see any explanation of what taking the lock earlier
> accomplishes.  Are you trying to avoid reading the revision-history twice?
> 
> Aaron

The problem is that the 'date' revision spec needs a lock. So if you
take out a lock earlier, it doesn't take out 2 locks.

It is just that 'in_history()' may actually want a lock on the
repository. So if we lock the whole command, we can eliminate
downloading a bunch of stuff, just to download it again later.

I'm +1 to adding a lock earlier, -1 to how it was specifically done.

John
=:->

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