[Xapian-tickets] [Xapian] #502: Use custom locking helper executable

[Xapian]

#502: Use custom locking helper executable
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 Reporter:  olly           |       Owner:  olly 
     Type:  enhancement    |      Status:  new  
 Priority:  normal         |   Milestone:  1.2.x
Component:  Backend-Chert  |     Version:  1.2.2
 Severity:  normal         |   Blockedby:       
 Platform:  All            |    Blocking:       
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 Here I noted that exec-ing our own custom statically linked helper
 executable instead of /bin/cat was quite a bit faster:

 http://article.gmane.org/gmane.comp.search.xapian.devel/519

 However we never got around to doing that.

 It's just occurred to me that there's an additional little win to be had
 in this case, at least on some platforms - if we have our own helper, we
 can move work like the closing of file descriptors to after the exec() and
 use vfork() instead of fork().  There's not a huge saving to be had from
 vfork() on a modern OS, but it can still be more efficient - for example:

 http://www.netbsd.org/docs/kernel/vfork.html

 On some platforms, vfork() may just be an alias for fork(), but there's no
 penalty to doing the work in the child that I can see, and it may still be
 a small win not to minimise modifications to pages shared with the parent.
 It also means close-on-exec file descriptors get closed for us, which may
 be more efficient.

 Marking as 1.2.x as this is ABI and API compatible.

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Ticket URL: <http://trac.xapian.org/ticket/502>
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