+++ /dev/null
-// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
-// vim: ts=8 sw=2 smarttab
-
-#include "Readahead.h"
-
-using namespace std;
-
-Readahead::Readahead()
- : m_trigger_requests(10),
- m_readahead_min_bytes(0),
- m_readahead_max_bytes(NO_LIMIT),
- m_alignments(),
- m_lock("Readahead::m_lock"),
- m_nr_consec_read(0),
- m_consec_read_bytes(0),
- m_last_pos(0),
- m_readahead_pos(0),
- m_readahead_trigger_pos(0),
- m_readahead_size(0),
- m_pending(0),
- m_pending_lock("Readahead::m_pending_lock") {
-}
-
-Readahead::~Readahead() {
-}
-
-Readahead::extent_t Readahead::update(const vector<extent_t>& extents, uint64_t limit) {
- m_lock.Lock();
- for (vector<extent_t>::const_iterator p = extents.begin(); p != extents.end(); ++p) {
- _observe_read(p->first, p->second);
- }
- if (m_readahead_pos >= limit|| m_last_pos >= limit) {
- m_lock.Unlock();
- return extent_t(0, 0);
- }
- pair<uint64_t, uint64_t> extent = _compute_readahead(limit);
- m_lock.Unlock();
- return extent;
-}
-
-Readahead::extent_t Readahead::update(uint64_t offset, uint64_t length, uint64_t limit) {
- m_lock.Lock();
- _observe_read(offset, length);
- if (m_readahead_pos >= limit || m_last_pos >= limit) {
- m_lock.Unlock();
- return extent_t(0, 0);
- }
- extent_t extent = _compute_readahead(limit);
- m_lock.Unlock();
- return extent;
-}
-
-void Readahead::_observe_read(uint64_t offset, uint64_t length) {
- if (offset == m_last_pos) {
- m_nr_consec_read++;
- m_consec_read_bytes += length;
- } else {
- m_nr_consec_read = 0;
- m_consec_read_bytes = 0;
- m_readahead_trigger_pos = 0;
- m_readahead_size = 0;
- m_readahead_pos = 0;
- }
- m_last_pos = offset + length;
-}
-
-Readahead::extent_t Readahead::_compute_readahead(uint64_t limit) {
- uint64_t readahead_offset = 0;
- uint64_t readahead_length = 0;
- if (m_nr_consec_read >= m_trigger_requests) {
- // currently reading sequentially
- if (m_last_pos >= m_readahead_trigger_pos) {
- // need to read ahead
- if (m_readahead_size == 0) {
- // initial readahead trigger
- m_readahead_size = m_consec_read_bytes;
- m_readahead_pos = m_last_pos;
- } else {
- // continuing readahead trigger
- m_readahead_size *= 2;
- if (m_last_pos > m_readahead_pos) {
- m_readahead_pos = m_last_pos;
- }
- }
- m_readahead_size = MAX(m_readahead_size, m_readahead_min_bytes);
- m_readahead_size = MIN(m_readahead_size, m_readahead_max_bytes);
- readahead_offset = m_readahead_pos;
- readahead_length = m_readahead_size;
-
- // Snap to the first alignment possible
- uint64_t readahead_end = readahead_offset + readahead_length;
- for (vector<uint64_t>::iterator p = m_alignments.begin(); p != m_alignments.end(); ++p) {
- // Align the readahead, if possible.
- uint64_t alignment = *p;
- uint64_t align_prev = readahead_end / alignment * alignment;
- uint64_t align_next = align_prev + alignment;
- uint64_t dist_prev = readahead_end - align_prev;
- uint64_t dist_next = align_next - readahead_end;
- if (dist_prev < readahead_length / 2 && dist_prev < dist_next) {
- // we can snap to the previous alignment point by a less than 50% reduction in size
- assert(align_prev > readahead_offset);
- readahead_length = align_prev - readahead_offset;
- break;
- } else if(dist_next < readahead_length / 2) {
- // we can snap to the next alignment point by a less than 50% increase in size
- assert(align_next > readahead_offset);
- readahead_length = align_next - readahead_offset;
- break;
- }
- // Note that m_readahead_size should remain unadjusted.
- }
-
- if (m_readahead_pos + readahead_length > limit) {
- readahead_length = limit - m_readahead_pos;
- }
-
- m_readahead_trigger_pos = m_readahead_pos + readahead_length / 2;
- m_readahead_pos += readahead_length;
- }
- }
- return extent_t(readahead_offset, readahead_length);
-}
-
-void Readahead::inc_pending(int count) {
- assert(count > 0);
- m_pending_lock.Lock();
- m_pending += count;
- m_pending_lock.Unlock();
-}
-
-void Readahead::dec_pending(int count) {
- assert(count > 0);
- m_pending_lock.Lock();
- assert(m_pending >= count);
- m_pending -= count;
- if (m_pending == 0) {
- std::list<Context *> pending_waiting(std::move(m_pending_waiting));
- m_pending_lock.Unlock();
-
- for (auto ctx : pending_waiting) {
- ctx->complete(0);
- }
- } else {
- m_pending_lock.Unlock();
- }
-}
-
-void Readahead::wait_for_pending() {
- C_SaferCond ctx;
- wait_for_pending(&ctx);
- ctx.wait();
-}
-
-void Readahead::wait_for_pending(Context *ctx) {
- m_pending_lock.Lock();
- if (m_pending > 0) {
- m_pending_lock.Unlock();
- m_pending_waiting.push_back(ctx);
- return;
- }
- m_pending_lock.Unlock();
-
- ctx->complete(0);
-}
-void Readahead::set_trigger_requests(int trigger_requests) {
- m_lock.Lock();
- m_trigger_requests = trigger_requests;
- m_lock.Unlock();
-}
-
-uint64_t Readahead::get_min_readahead_size(void) {
- Mutex::Locker lock(m_lock);
- return m_readahead_min_bytes;
-}
-
-uint64_t Readahead::get_max_readahead_size(void) {
- Mutex::Locker lock(m_lock);
- return m_readahead_max_bytes;
-}
-
-void Readahead::set_min_readahead_size(uint64_t min_readahead_size) {
- m_lock.Lock();
- m_readahead_min_bytes = min_readahead_size;
- m_lock.Unlock();
-}
-
-void Readahead::set_max_readahead_size(uint64_t max_readahead_size) {
- m_lock.Lock();
- m_readahead_max_bytes = max_readahead_size;
- m_lock.Unlock();
-}
-
-void Readahead::set_alignments(const vector<uint64_t> &alignments) {
- m_lock.Lock();
- m_alignments = alignments;
- m_lock.Unlock();
-}
Code Review / stor4nfv.git / blobdiff