From 399d0026fbcf4df1be4604d68d2615285c0f1da1 Mon Sep 17 00:00:00 2001
From: Vladimir Davydov <vdavydov@tarantool.org>
Date: Mon, 18 Jul 2022 11:18:13 +0300
Subject: [PATCH] memtx: rename MemtxAllocator::snapshot_version to
read_view_version
Because we will use this version for user read views, not just
snapshots. Comments are updated as well.
NO_DOC=refactoring
NO_TEST=refactoring
NO_CHANGELOG=refactoring
---
src/box/memtx_allocator.h | 35 +++++++++++++++++++++--------------
1 file changed, 21 insertions(+), 14 deletions(-)
diff --git a/src/box/memtx_allocator.h b/src/box/memtx_allocator.h
index a1caa94224..b72b74b21f 100644
--- a/src/box/memtx_allocator.h
+++ b/src/box/memtx_allocator.h
@@ -40,14 +40,17 @@
*/
struct memtx_tuple {
/*
- * sic: the header of the tuple is used
- * to store a free list pointer in smfree_delayed.
- * Please don't change it without understanding
- * how smfree_delayed and snapshotting COW works.
+ * Sic: The header of the tuple is used to store a link in
+ * a tuple garbage collection list. Please don't change it
+ * without understanding how tuple garbage collection and
+ * copy-on-write mechanisms work.
*/
union {
struct {
- /** Snapshot generation version. */
+ /**
+ * Most recent read view's version at the time
+ * when the tuple was allocated.
+ */
uint32_t version;
/** Base tuple class. */
struct tuple base;
@@ -93,7 +96,7 @@ class MemtxAllocator {
static ReadView *open_read_view(struct memtx_read_view_opts opts)
{
(void)opts;
- snapshot_version++;
+ read_view_version++;
delayed_free_mode++;
return nullptr;
}
@@ -119,23 +122,23 @@ class MemtxAllocator {
(struct memtx_tuple *)alloc(total);
if (memtx_tuple == NULL)
return NULL;
- memtx_tuple->version = snapshot_version;
+ memtx_tuple->version = read_view_version;
return &memtx_tuple->base;
}
/**
* Free a tuple allocated with alloc_tuple().
*
- * The tuple is freed immediately if there's no snapshot that may use
+ * The tuple is freed immediately if there's no read view that may use
* it. Otherwise, it's put in the garbage collection list to be free as
- * soon as the last snapshot using it is destroyed.
+ * soon as the last read view using it is destroyed.
*/
static void free_tuple(struct tuple *tuple)
{
struct memtx_tuple *memtx_tuple = container_of(
tuple, struct memtx_tuple, base);
if (delayed_free_mode == 0 ||
- memtx_tuple->version == snapshot_version ||
+ memtx_tuple->version == read_view_version ||
tuple_has_flag(tuple, TUPLE_IS_TEMPORARY)) {
immediate_free_tuple(memtx_tuple);
} else {
@@ -182,7 +185,7 @@ class MemtxAllocator {
/**
* Tuple garbage collection list. Contains tuples that were not freed
- * immediately because they are currently in use by a snapshot.
+ * immediately because they are currently in use by a read view.
*/
static struct stailq gc;
/**
@@ -190,8 +193,12 @@ class MemtxAllocator {
* open_read_view() is delayed until close_read_view() is called.
*/
static uint32_t delayed_free_mode;
- /** Incremented with each next snapshot. */
- static uint32_t snapshot_version;
+ /**
+ * Most recent read view's version.
+ *
+ * Incremented with each open read view. Not supposed to wrap around.
+ */
+ static uint32_t read_view_version;
};
template<class Allocator>
@@ -201,7 +208,7 @@ template<class Allocator>
uint32_t MemtxAllocator<Allocator>::delayed_free_mode;
template<class Allocator>
-uint32_t MemtxAllocator<Allocator>::snapshot_version;
+uint32_t MemtxAllocator<Allocator>::read_view_version;
void
memtx_allocators_init(struct allocator_settings *settings);
--
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