[mythtv-commits] Ticket #9458: [PATCH] posix_fadvice usage
MythTV
noreply at mythtv.org
Fri May 13 21:37:49 UTC 2011
#9458: [PATCH] posix_fadvice usage
----------------------------------------+----------------------------
Reporter: jiri.fojtasek@… | Owner: danielk
Type: Patch - Bug Fix | Status: closed
Priority: minor | Milestone: 0.25
Component: MythTV - General | Version: Trunk Head
Severity: medium | Resolution: Fixed
Keywords: | Ticket locked: 0
----------------------------------------+----------------------------
--version Output:
----------------------------------------+----------------------------
Changes (by danielk):
* status: assigned => closed
* resolution: => Fixed
Comment:
Most of the issues here were dealt with by [e4c5909]. The rest would seem
to be a bad idea for the same reason previous fadvise patches were a bad
idea. First, linux interprets the DONTNEED calls globally, so if one
application says it won't need the data and another says it will, the data
can get thrown out of cache repeatedly. The other problem is that WILLNEED
doesn't tell the OS to start reading the data in the background so a
future read will execute more quickly, it actually blocks while reading in
the entire amount of data that we're telling it we will need in the
future. All this means the only really useful thing we can do with fadvise
is to issue the SEQUENTIAL one, and there are a couple cases where it
makes sense to do a small WILLNEED just to avoid starting playback and
then pausing (it's better to just take a few milliseconds longer start
delivering frames than to deliver a few and then pause for a few
milliseconds.)
--
Ticket URL: <http://code.mythtv.org/trac/ticket/9458#comment:5>
MythTV <http://code.mythtv.org/trac>
MythTV Media Center
More information about the mythtv-commits
mailing list