Feature #9957: librados: add fadvise op - Ceph - Ceph

Feature #9957

librados: add fadvise op

Added by Sage Weil over 8 years ago. Updated over 8 years ago.

Status:

Resolved

Priority:

Normal

Assignee:

Category:

Target version:

v.actually91

% Done:

Source:

Community (dev)

Tags:

Backport:

Reviewed:

Affected Versions:

Pull request ID:

Description

Add an fadvise operation to ObjectOperation. Mirror posix_fadvise(2).

Add it right around here: https://github.com/ceph/ceph/blob/master/src/include/rados/librados.hpp#L338

Probably use these hints:

DONTNEED   don't cache
RANDOM     don't do readahead
SEQUENTIAL will read/write more
WILLNEED   positive indication that we should cache something

but not

? NOREUSE? this is sort of the same as DONTNEED?

History

#1 Updated by Sage Weil over 8 years ago

Description updated (diff)
Source changed from other to Community (dev)

#2 Updated by Sage Weil over 8 years ago

Target version deleted (~~0.90~~)

#3 Updated by jianpeng ma over 8 years ago

From the man posix_advise & kernel related code:
In kernels before 2.6.18, POSIX_FADV_NOREUSE had the same semantics as POSIX_FADV_WILLNEED. This was probably a bug; since kernel 2.6.18, this flag is a no-op.

So we can remove this flag. Except those flags
DONTNEED don't cache
RANDOM don't do readahead
SEQUENTIAL will read/write more
WILLNEED positive indication that we should cache something

We should add NORMAL. Because RANDOM/SEQUENTIAL will effect whole file(expect we close and reopen this flag), for two flags don't care the offset/length.