[mythtv-commits] Ticket #9458: [patch] posix_fadvice usage
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Fri Jan 7 18:39:00 UTC 2011
#9458: [patch] posix_fadvice usage
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Reporter: jiri.fojtasek@… | Owner: danielk
Type: Patch - Bug Fix | Status: assigned
Priority: minor | Milestone: 0.25
Component: MythTV - General | Version: Trunk Head
Severity: medium | Resolution:
Keywords: | Ticket locked: 0
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Changes (by danielk):
* owner: => danielk
* status: new => assigned
Comment:
Jiri, I noticed that one of the fixes was signed by a "--setra". Is there
a thread somewhere with longer explanations of each of the changes? The
main thing I see here is that these advise calls appear to be interpreted
globally rather than per file descriptor. i.e. if process A is reading
file X on fd 2 at location 1024 and process B is writing to X fd 3 then
when B issues a POSIX_FADV_WONTNEED for the data before location 2048,
process A now needs to read from the disk rather than reading from the
cache. This would be caused by the OS is not being smart enough to realize
that even if process B doesn't plan to read the file soon, process A is
reading the file with the SEQUENTIAL attribute and will soon read bytes
1025 through 2048.
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Ticket URL: <http://code.mythtv.org/trac/ticket/9458#comment:1>
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