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Feature #12915

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Translate fadvise flag NOCACHE into DONTNEED if first access object

Added by Loïc Dachary over 8 years ago.

Status:
In Progress
Priority:
Normal
Assignee:
-
Category:
-
Target version:
-
% Done:

0%

Source:
other
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Backport:
Reviewed:
Affected Versions:
Pull request ID:

Description

https://github.com/ceph/ceph/pull/3868

The mean of LIBRADOS_OP_FLAG_FADVISE_NOCACHE is only this client don't
need data in the future. For filestore, it hope if no data found in page
cache it should use directio. But at present, filesystem don't handle
this.
So we use a tricky method that if can't find object in cache of
ObjectContext which mean in the shorttime no one access this object.
In that case we add DONTNEED flag if op has NOCACHE.
Although this method isn't exactly. But at some case it can work and
don't affect others.

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