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commitlog: Make pre-allocation drop O_DSYNC while pre-filling

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Refs #7794

Iff we need to pre-fill segment file ni O_DSYNC mode, we should
drop this for the pre-fill, to avoid issuing flushes until the file
is filled. Done by temporarily closing, re-opening in "normal" mode,
filling, then re-opening.

v2:
* More comment
v3:
* Add missing flush
v4:
* comment
v5:
* Split coroutine and fix into separate patches
This commit is contained in:
Calle Wilund
2021-03-15 09:32:01 +00:00
parent ae3b8e6fdf
commit 48ca01c3ab
2 changed files with 38 additions and 0 deletions
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9
db/commitlog/commitlog.cc
View File

@@ -1418,6 +1418,13 @@ future<db::commitlog::segment_manager::sseg_ptr> db::commitlog::segment_manager:
clogger.trace("Pre-writing {} of {} KB to segment {}", (max_size - existing_size)/1024, max_size/1024, filename);
// re-open without o_dsync for pre-alloc. The reason/rationale
// being that we want automatic (meta)data sync from O_DSYNC for when
// we do actual CL flushes, but here it would just result in
// data being committed before we've reached eof/finished writing.
// Again an argument for sendfile-like constructs I guess...
co_await f.close();
f = co_await open_file_dma(filename, flags & open_flags(~int(open_flags::dsync)), opt);
co_await f.allocate(existing_size, max_size - existing_size);
static constexpr size_t buf_size = 4 * segment::alignment;
@@ -1443,6 +1450,8 @@ future<db::commitlog::segment_manager::sseg_ptr> db::commitlog::segment_manager:
// sync metadata (size/written)
co_await f.flush();
co_await f.close();
f = co_await open_file_dma(filename, flags, opt);
}
} else {
co_await f.truncate(max_size);

29
test/boost/commitlog_test.cc
View File

@@ -30,6 +30,7 @@
#include <set>
#include <seastar/testing/test_case.hh>
#include <seastar/core/coroutine.hh>
#include <seastar/core/future-util.hh>
#include <seastar/core/do_with.hh>
#include <seastar/core/scollectd_api.hh>
@@ -719,3 +720,31 @@ SEASTAR_TEST_CASE(test_commitlog_add_entries) {
});
}
SEASTAR_TEST_CASE(test_commitlog_new_segment_odsync){
commitlog::config cfg;
cfg.commitlog_segment_size_in_mb = 1;
cfg.use_o_dsync = true;
return cl_test(cfg, [](commitlog& log) -> future<> {
auto uuid = utils::UUID_gen::get_time_UUID();
rp_set set;
while (set.size() <= 1) {
sstring tmp = "hej bubba cow";
rp_handle h = co_await log.add_mutation(uuid, tmp.size(), db::commitlog::force_sync::no, [tmp](db::commitlog::output& dst) {
dst.write(tmp.data(), tmp.size());
});
set.put(std::move(h));
}
auto names = log.get_active_segment_names();
BOOST_REQUIRE(names.size() > 1);
// check that all the segments are pre-allocated.
for (auto& name : names) {
auto f = co_await seastar::open_file_dma(name, seastar::open_flags::ro);
auto s = co_await f.size();
co_await f.close();
BOOST_CHECK_EQUAL(s, 1024u*1024u);
}
});
}