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// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
// vim: ts=8 sw=2 smarttab
//
// A simple allocator that just hands out space from the next empty zone. This
// is temporary, just to get the simplest append-only write workload to work.
//
// Copyright (C) 2020 Abutalib Aghayev
//
#include "ZonedAllocator.h"
#include "bluestore_types.h"
#include "zoned_types.h"
#include "common/debug.h"
#define dout_context cct
#define dout_subsys ceph_subsys_bluestore
#undef dout_prefix
#define dout_prefix *_dout << "ZonedAllocator(" << this << ") " << __func__ << " "
ZonedAllocator::ZonedAllocator(CephContext* cct,
int64_t size,
int64_t blk_size,
int64_t _zone_size,
int64_t _first_sequential_zone,
std::string_view name)
: Allocator(name, size, blk_size),
cct(cct),
size(size),
conventional_size(_first_sequential_zone * _zone_size),
sequential_size(size - conventional_size),
num_sequential_free(0),
block_size(blk_size),
zone_size(_zone_size),
first_seq_zone_num(_first_sequential_zone),
starting_zone_num(first_seq_zone_num),
num_zones(size / zone_size)
{
ldout(cct, 10) << " size 0x" << std::hex << size
<< ", zone size 0x" << zone_size << std::dec
<< ", number of zones 0x" << num_zones
<< ", first sequential zone 0x" << starting_zone_num
<< ", sequential size 0x" << sequential_size
<< std::dec
<< dendl;
ceph_assert(size % zone_size == 0);
zone_states.resize(num_zones);
}
ZonedAllocator::~ZonedAllocator()
{
}
int64_t ZonedAllocator::allocate(
uint64_t want_size,
uint64_t alloc_unit,
uint64_t max_alloc_size,
int64_t hint,
PExtentVector *extents)
{
std::lock_guard l(lock);
ceph_assert(want_size % 4096 == 0);
ldout(cct, 10) << " trying to allocate 0x"
<< std::hex << want_size << std::dec << dendl;
uint64_t left = num_zones - first_seq_zone_num;
uint64_t zone_num = starting_zone_num;
for ( ; left > 0; ++zone_num, --left) {
if (zone_num == num_zones) {
zone_num = first_seq_zone_num;
}
if (zone_num == cleaning_zone) {
ldout(cct, 10) << " skipping zone 0x" << std::hex << zone_num
<< " because we are cleaning it" << std::dec << dendl;
continue;
}
if (!fits(want_size, zone_num)) {
ldout(cct, 10) << " skipping zone 0x" << std::hex << zone_num
<< " because there is not enough space: "
<< " want_size = 0x" << want_size
<< " available = 0x" << get_remaining_space(zone_num)
<< std::dec
<< dendl;
continue;
}
break;
}
if (left == 0) {
ldout(cct, 10) << " failed to allocate" << dendl;
return -ENOSPC;
}
uint64_t offset = get_offset(zone_num);
ldout(cct, 10) << " moving zone 0x" << std::hex
<< zone_num << " write pointer from 0x" << offset
<< " -> 0x" << offset + want_size
<< std::dec << dendl;
increment_write_pointer(zone_num, want_size);
num_sequential_free -= want_size;
if (get_remaining_space(zone_num) == 0) {
starting_zone_num = zone_num + 1;
}
ldout(cct, 10) << " allocated 0x" << std::hex << offset << "~" << want_size
<< " from zone 0x" << zone_num
<< " and zone offset 0x" << (offset % zone_size)
<< std::dec << dendl;
extents->emplace_back(bluestore_pextent_t(offset, want_size));
return want_size;
}
void ZonedAllocator::release(const interval_set<uint64_t>& release_set)
{
std::lock_guard l(lock);
for (auto p = cbegin(release_set); p != cend(release_set); ++p) {
auto offset = p.get_start();
auto length = p.get_len();
uint64_t zone_num = offset / zone_size;
ldout(cct, 10) << " 0x" << std::hex << offset << "~" << length
<< " from zone 0x" << zone_num << std::dec << dendl;
uint64_t num_dead = std::min(zone_size - offset % zone_size, length);
for ( ; length; ++zone_num) {
increment_num_dead_bytes(zone_num, num_dead);
length -= num_dead;
num_dead = std::min(zone_size, length);
}
}
}
uint64_t ZonedAllocator::get_free()
{
return num_sequential_free;
}
void ZonedAllocator::dump()
{
std::lock_guard l(lock);
}
void ZonedAllocator::foreach(
std::function<void(uint64_t offset, uint64_t length)> notify)
{
std::lock_guard l(lock);
}
void ZonedAllocator::init_from_zone_pointers(
std::vector<zone_state_t> &&_zone_states)
{
// this is called once, based on the device's zone pointers
std::lock_guard l(lock);
ldout(cct, 10) << dendl;
zone_states = std::move(_zone_states);
num_sequential_free = 0;
for (size_t i = first_seq_zone_num; i < num_zones; ++i) {
num_sequential_free += zone_size - (zone_states[i].write_pointer % zone_size);
}
ldout(cct, 10) << "free 0x" << std::hex << num_sequential_free
<< " / 0x" << sequential_size << std::dec
<< dendl;
}
int64_t ZonedAllocator::pick_zone_to_clean(float min_score, uint64_t min_saved)
{
std::lock_guard l(lock);
int32_t best = -1;
float best_score = 0.0;
for (size_t i = first_seq_zone_num; i < num_zones; ++i) {
// value (score) = benefit / cost
// benefit = how much net free space we'll get (dead bytes)
// cost = how many bytes we'll have to rewrite (live bytes)
// avoid divide by zero on a zone with no live bytes
float score =
(float)zone_states[i].num_dead_bytes /
(float)(zone_states[i].get_num_live_bytes() + 1);
if (score > 0) {
ldout(cct, 20) << " zone 0x" << std::hex << i
<< " dead 0x" << zone_states[i].num_dead_bytes
<< " score " << score
<< dendl;
}
if (zone_states[i].num_dead_bytes < min_saved) {
continue;
}
if (best < 0 || score > best_score) {
best = i;
best_score = score;
}
}
if (best_score >= min_score) {
ldout(cct, 10) << " zone 0x" << std::hex << best << " with score " << best_score
<< ": 0x" << zone_states[best].num_dead_bytes
<< " dead and 0x"
<< zone_states[best].write_pointer - zone_states[best].num_dead_bytes
<< " live bytes" << std::dec << dendl;
} else if (best > 0) {
ldout(cct, 10) << " zone 0x" << std::hex << best << " with score " << best_score
<< ": 0x" << zone_states[best].num_dead_bytes
<< " dead and 0x"
<< zone_states[best].write_pointer - zone_states[best].num_dead_bytes
<< " live bytes" << std::dec
<< " but below min_score " << min_score
<< dendl;
best = -1;
} else {
ldout(cct, 10) << " no zones found that are good cleaning candidates" << dendl;
}
return best;
}
void ZonedAllocator::reset_zone(uint32_t zone)
{
num_sequential_free += zone_states[zone].write_pointer;
zone_states[zone].reset();
}
bool ZonedAllocator::low_on_space(void)
{
std::lock_guard l(lock);
double free_ratio = static_cast<double>(num_sequential_free) / sequential_size;
ldout(cct, 10) << " free 0x" << std::hex << num_sequential_free
<< "/ 0x" << sequential_size << std::dec
<< ", free ratio is " << free_ratio << dendl;
ceph_assert(num_sequential_free <= (int64_t)sequential_size);
// TODO: make 0.25 tunable
return free_ratio <= 0.25;
}
void ZonedAllocator::shutdown()
{
ldout(cct, 1) << dendl;
}
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