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c95dd67d11
It is a read-through cache of a file. Will be used to cache contents of the promoted index area from the index file. Currently, cached pages are evicted manually using the invalidate_*() method family, or when the object is destroyed. The cached_file represents a subset of the file. The reason for this is to satisfy two requirements. One is that we have a page-aligned caching, where pages are aligned relative to the start of the underlying file. This matches requirements of the seastar I/O engine on I/O requests. Another requirement is to have an effective way to populate the cache using an unaligned buffer which starts in the middle of the file when we know that we won't need to access bytes located before the buffer's position. See populate_front(). If we couldn't assume that, we wouldn't be able to insert an unaligned buffer into the cache.
327 lines
10 KiB
C++
327 lines
10 KiB
C++
/*
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* Copyright (C) 2020 ScyllaDB
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*/
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/*
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* This file is part of Scylla.
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*
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* Scylla is free software: you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Scylla is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Scylla. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <seastar/testing/test_case.hh>
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#include <seastar/testing/thread_test_case.hh>
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#include <seastar/core/iostream.hh>
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#include <seastar/core/fstream.hh>
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#include <seastar/core/file.hh>
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#include <seastar/core/reactor.hh>
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#include <seastar/util/defer.hh>
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#include "test/lib/random_utils.hh"
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#include "test/lib/log.hh"
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#include "test/lib/tmpdir.hh"
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#include "test/lib/reader_permit.hh"
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#include "utils/cached_file.hh"
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using namespace seastar;
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static sstring read_to_string(cached_file::stream& s, size_t limit = std::numeric_limits<size_t>::max()) {
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sstring b;
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while (auto buf = s.next().get0()) {
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b += sstring(buf.get(), buf.size());
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if (b.size() >= limit) {
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break;
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}
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}
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return b.substr(0, limit);
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}
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static sstring read_to_string(cached_file& cf, size_t off, size_t limit = std::numeric_limits<size_t>::max()) {
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auto s = cf.read(off, default_priority_class());
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return read_to_string(s, limit);
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}
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struct test_file {
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tmpdir dir;
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file f;
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sstring contents;
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~test_file() {
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f.close().get();
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}
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};
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test_file make_test_file(size_t size) {
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tmpdir dir;
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auto contents = tests::random::get_sstring(size);
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auto path = dir.path() / "file";
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file f = open_file_dma(path.c_str(), open_flags::create | open_flags::rw).get0();
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testlog.debug("file contents: {}", contents);
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output_stream<char> out = make_file_output_stream(f).get0();
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auto close_out = defer([&] { out.close().get(); });
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out.write(contents.begin(), contents.size()).get();
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out.flush().get();
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f = open_file_dma(path.c_str(), open_flags::ro).get0();
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return test_file{
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.dir = std::move(dir),
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.f = std::move(f),
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.contents = std::move(contents)
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};
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}
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SEASTAR_THREAD_TEST_CASE(test_reading_from_small_file) {
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test_file tf = make_test_file(1024);
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{
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cached_file::metrics metrics;
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cached_file cf(tf.f, tests::make_permit(), metrics, 0, tf.contents.size());
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{
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BOOST_REQUIRE_EQUAL(tf.contents, read_to_string(cf, 0));
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BOOST_REQUIRE_EQUAL(1024, metrics.cached_bytes);
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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BOOST_REQUIRE_EQUAL(0, metrics.page_hits);
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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}
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{
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BOOST_REQUIRE_EQUAL(tf.contents.substr(2), read_to_string(cf, 2));
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BOOST_REQUIRE_EQUAL(1024, metrics.cached_bytes);
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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BOOST_REQUIRE_EQUAL(1, metrics.page_hits); // change here
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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}
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{
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BOOST_REQUIRE_EQUAL(sstring(), read_to_string(cf, 3000));
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// no change
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BOOST_REQUIRE_EQUAL(1024, metrics.cached_bytes);
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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BOOST_REQUIRE_EQUAL(1, metrics.page_hits);
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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}
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}
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{
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size_t off = 100;
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cached_file::metrics metrics;
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cached_file cf(tf.f, tests::make_permit(), metrics, off, tf.contents.size() - off);
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BOOST_REQUIRE_EQUAL(tf.contents.substr(off), read_to_string(cf, 0));
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BOOST_REQUIRE_EQUAL(tf.contents.substr(off + 2), read_to_string(cf, 2));
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BOOST_REQUIRE_EQUAL(sstring(), read_to_string(cf, 3000));
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}
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}
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SEASTAR_THREAD_TEST_CASE(test_invalidation) {
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auto page_size = cached_file::page_size;
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test_file tf = make_test_file(page_size * 2);
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cached_file::metrics metrics;
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cached_file cf(tf.f, tests::make_permit(), metrics, 0, page_size * 2);
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// Reads one page, half of the first page and half of the second page.
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auto read = [&] {
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BOOST_REQUIRE_EQUAL(
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tf.contents.substr(page_size / 2, page_size),
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read_to_string(cf, page_size / 2, page_size));
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};
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read();
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BOOST_REQUIRE_EQUAL(2, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(2, metrics.page_misses);
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metrics = {};
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, page_size / 2);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, page_size - 1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, page_size);
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BOOST_REQUIRE_EQUAL(1, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(1, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(page_size, page_size + 1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(page_size, page_size + page_size);
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BOOST_REQUIRE_EQUAL(1, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(1, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, page_size * 3);
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BOOST_REQUIRE_EQUAL(2, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(2, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(0, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most_front(0);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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metrics = {};
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cf.invalidate_at_most_front(1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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metrics = {};
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cf.invalidate_at_most_front(page_size);
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BOOST_REQUIRE_EQUAL(1, metrics.page_evictions);
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metrics = {};
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cf.invalidate_at_most_front(page_size * 2);
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BOOST_REQUIRE_EQUAL(1, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(2, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(0, metrics.page_hits);
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}
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SEASTAR_THREAD_TEST_CASE(test_invalidation_skewed_cached_file) {
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auto page_size = cached_file::page_size;
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test_file tf = make_test_file(page_size * 3);
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size_t offset = page_size / 2;
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cached_file::metrics metrics;
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cached_file cf(tf.f, tests::make_permit(), metrics, offset, page_size * 2);
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// Reads one page, half of the first page and half of the second page.
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auto read = [&] {
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BOOST_REQUIRE_EQUAL(
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tf.contents.substr(offset, page_size),
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read_to_string(cf, 0, page_size));
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};
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read();
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BOOST_REQUIRE_EQUAL(2, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(2, metrics.page_misses);
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metrics = {};
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, 1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(1, page_size - align_up(offset, page_size) - 1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, page_size);
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BOOST_REQUIRE_EQUAL(1, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(1, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(1, page_size);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(1, align_up(offset, page_size) - offset + page_size);
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BOOST_REQUIRE_EQUAL(1, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(1, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(1, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(1, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(1, align_up(offset, page_size) - offset + page_size - 1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(0, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(0, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(2, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most(0, page_size * 3);
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BOOST_REQUIRE_EQUAL(2, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(2, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(0, metrics.page_hits);
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metrics = {};
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cf.invalidate_at_most_front(0);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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metrics = {};
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cf.invalidate_at_most_front(1);
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BOOST_REQUIRE_EQUAL(0, metrics.page_evictions);
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metrics = {};
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cf.invalidate_at_most_front(align_up(offset, page_size) - offset + page_size);
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BOOST_REQUIRE_EQUAL(2, metrics.page_evictions);
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read();
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metrics = {};
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cf.invalidate_at_most_front(page_size * 3);
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BOOST_REQUIRE_EQUAL(2, metrics.page_evictions);
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read();
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BOOST_REQUIRE_EQUAL(2, metrics.page_misses);
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BOOST_REQUIRE_EQUAL(2, metrics.page_populations);
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BOOST_REQUIRE_EQUAL(0, metrics.page_hits);
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}
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