Re: Reload VM hint? (James Bucanek)
Re: Reload VM hint? (James Bucanek)
- Subject: Re: Reload VM hint? (James Bucanek)
- From: Sam Vaughan <email@hidden>
- Date: Sun, 3 Jun 2007 13:17:25 +1000
On 01/06/2007, at 5:04 AM, James Bucanek <email@hidden>:
I hadn't thought of that, and that's an excellent suggestion
(thanks also extended to Brian and Matt). The source file data
is only read once, so at least I can eliminate that from being
cashed. Come to think of it, that might improve my overall
performance since the reading the source file blocks also
competes with the caching of my database file blocks.
There's an even better reason why F_NOCACHE will probably improve
your code's performance. Provided that you do as Quinn suggests with
respect to alignment, it will cause the I/O to go directly to/from
your user space buffer, removing the additional copy that happens in
the buffered I/O case. This is why it's called "direct I/O" on most
other platforms, where the O_DIRECT flag is used at file open time to
enable it.
Sam
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