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bees: use readahead instead of posix_fadvise

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Other btrfs utils use readahead() not posix_fadvise().

There does not appear to be a performance or correctness difference
between the three (none, posix_fadvise, or readahead()).

Signed-off-by: Zygo Blaxell <bees@furryterror.org>
This commit is contained in:
Zygo Blaxell 2018-07-08 10:33:30 -04:00
parent 041ad717a5
commit 96eb100ded
2 changed files with 5 additions and 5 deletions
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2
src/bees-context.cc
View File

@ -313,7 +313,7 @@ BeesContext::scan_one_extent(const BeesFileRange &bfr, const Extent &e)
}
// OK we need to read extent now
posix_fadvise(bfr.fd(), bfr.begin(), bfr.size(), POSIX_FADV_WILLNEED);
readahead(bfr.fd(), bfr.begin(), bfr.size());
map<off_t, pair<BeesHash, BeesAddress>> insert_map;
set<off_t> noinsert_set;

8
src/bees-types.cc
View File

@ -386,8 +386,8 @@ BeesRangePair::grow(shared_ptr<BeesContext> ctx, bool constrained)
BEESTRACE("e_second " << e_second);
// Preread entire extent
posix_fadvise(second.fd(), e_second.begin(), e_second.size(), POSIX_FADV_WILLNEED);
posix_fadvise(first.fd(), e_second.begin() + first.begin() - second.begin(), e_second.size(), POSIX_FADV_WILLNEED);
readahead(second.fd(), e_second.begin(), e_second.size());
readahead(first.fd(), e_second.begin() + first.begin() - second.begin(), e_second.size());
auto hash_table = ctx->hash_table();
@ -406,7 +406,7 @@ BeesRangePair::grow(shared_ptr<BeesContext> ctx, bool constrained)
BEESCOUNT(pairbackward_hole);
break;
}
posix_fadvise(second.fd(), e_second.begin(), e_second.size(), POSIX_FADV_WILLNEED);
readahead(second.fd(), e_second.begin(), e_second.size());
#else
// This tends to repeatedly process extents that were recently processed.
// We tend to catch duplicate blocks early since we scan them forwards.
@ -515,7 +515,7 @@ BeesRangePair::grow(shared_ptr<BeesContext> ctx, bool constrained)
BEESCOUNT(pairforward_hole);
break;
}
posix_fadvise(second.fd(), e_second.begin(), e_second.size(), POSIX_FADV_WILLNEED);
readahead(second.fd(), e_second.begin(), e_second.size());
}
BEESCOUNT(pairforward_try);