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perf: optimize the only block case in Cache::writeContiguous() (#4679)

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Dmitry Antipov 2023-01-30 21:04:40 +03:00 committed by GitHub
parent 18277a6dd0
commit 52d49b84eb
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1 changed files with 23 additions and 14 deletions
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15
libtransmission/cache.cc
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@ -71,8 +71,15 @@ std::pair<Cache::CIter, Cache::CIter> Cache::findContiguous(CIter const begin, C
int Cache::writeContiguous(CIter const begin, CIter const end) const int Cache::writeContiguous(CIter const begin, CIter const end) const
{ {
// join the blocks together into contiguous memory `buf` // The most common case without an extra data copy.
auto const* towrite = begin->buf.get();
// Contiguous area to join more than one block, if any.
auto buf = std::vector<uint8_t>{}; auto buf = std::vector<uint8_t>{};
if (end - begin > 1)
{
// Yes, there are.
auto const buflen = std::accumulate( auto const buflen = std::accumulate(
begin, begin,
end, end,
@ -86,6 +93,8 @@ int Cache::writeContiguous(CIter const begin, CIter const end) const
buf.insert(std::end(buf), std::begin(*iter->buf), std::end(*iter->buf)); buf.insert(std::end(buf), std::begin(*iter->buf), std::end(*iter->buf));
} }
TR_ASSERT(std::size(buf) == buflen); TR_ASSERT(std::size(buf) == buflen);
towrite = &buf;
}
// save it // save it
auto const& [torrent_id, block] = begin->key; auto const& [torrent_id, block] = begin->key;
@ -97,13 +106,13 @@ int Cache::writeContiguous(CIter const begin, CIter const end) const
auto const loc = tor->blockLoc(block); auto const loc = tor->blockLoc(block);
if (auto const err = tr_ioWrite(tor, loc, std::size(buf), std::data(buf)); err != 0) if (auto const err = tr_ioWrite(tor, loc, std::size(*towrite), std::data(*towrite)); err != 0)
{ {
return err; return err;
} }
++disk_writes_; ++disk_writes_;
disk_write_bytes_ += std::size(buf); disk_write_bytes_ += std::size(*towrite);
return {}; return {};
} }