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pma: cleanup
comment cleanup and removal of dead code
This commit is contained in:
barter-simsum
parent
46ffb737ac
commit
c859a5f577
@ -341,7 +341,7 @@ struct BT_state {
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int data_fd;
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char *path;
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void *fixaddr;
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/* ;;: TODO: refactor ->map to be a (BT_page *) */
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/* TODO: refactor ->map to be a (BT_page *) */
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BYTE *map;
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BT_meta *meta_pages[2]; /* double buffered */
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pgno_t file_size_p; /* the size of the pma file in pages */
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@ -379,62 +379,9 @@ struct BT_findpath {
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static BT_page *
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_node_get(BT_state *state, pgno_t pgno)
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{
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/* TODO: eventually, once we can store more than 2M of nodes, this will need
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to reference the meta page's blk_base array to determine where a node is
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mapped. i.e:
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- receive pgno
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- find first pgno in blk_base that exceeds pgno : i
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- sector that contains node is i-1
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- appropriately offset into i-1th fixed size partition: 2M, 8M, 16M, ...
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*/
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/* for now, this works because the 2M sector is at the beginning of both the
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memory arena and pma file
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*/
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/* TODO: wrap in DEBUG macro a looping assert to confirm the given pgno is
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contained within a node partition */
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assert(pgno >= BT_NUMMETAS);
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#if 0
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BT_meta *meta = state->meta_pages[state->which];
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/* find the partition that contains pgno */
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size_t partition_idx = 0;
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for (;; partition_idx++) {
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assert(partition_idx < BT_NUMPARTS);
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pgno_t partition_beg = meta->blk_base[partition_idx];
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pgno_t partition_end = partition_beg + B2PAGES(BLK_BASE_LENS_b[partition_idx]);
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if (partition_end > pgno) {
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assert(partition_beg <= pgno);
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break;
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}
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}
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/* ;;: hmm. is there something wrong here? No, I don't think so.
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On resume (reading a persistent file):
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1) mmap the node partitions.
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- (read the offset stored in meta->blk_base)
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- mmap the offset + corresponding length of the pma file next to the end
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of the last partition in the memory arena. (in memory, nodes are all
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stored at the lowest addresses)
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calls to _node_get are given a pgno in the persistent file:
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1) find the partition that contains this pgno
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2) Do math on the pgno + found partition to find the memory address it's
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mapped to and return that as a BT_page *
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*** We do, however, need to be sure we aren't cheating anywhere and using a
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*** page offset into the memory arena and calling _node_get on it. That
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*** would technically work for the first partition. It will NOT work for any
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*** other partition. Not sure if we are doing that anywhere currently.
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*/
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#endif
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return FO2PA(state->map, pgno);
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}
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@ -442,7 +389,6 @@ _node_get(BT_state *state, pgno_t pgno)
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static pgno_t
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_fo_get(BT_state *state, BT_page *node)
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{
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/* ;;: This may need to be fixed to accommodate partition striping */
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uintptr_t vaddr = (uintptr_t)node;
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uintptr_t start = (uintptr_t)state->map;
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return BY2FO(vaddr - start);
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@ -535,8 +481,6 @@ _nlist_grow(BT_state *state)
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}
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pgno_t memoff_p = B2PAGES(targ - BT_MAPADDR);
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/* ;;: tmp assert. debugging. */
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assert(&((BT_page *)state->map)[memoff_p] == (BT_page *)targ);
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/* add the partition to the nlist */
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_nlist_insertn(state,
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@ -659,7 +603,7 @@ _bt_nalloc(BT_state *state)
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/* make node writable */
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if (mprotect(ret, sizeof(BT_page), BT_PROT_DIRTY) != 0) {
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DPRINTF("mprotect of node: %p failed with %s", ret, strerror(errno));
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abort(); /* ;;: https://stackoverflow.com/questions/6862825/getting-cannot-allocate-memory-error */
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abort();
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}
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return ret;
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@ -1078,7 +1022,6 @@ _mlist_insert(BT_state *state, void *lo, void *hi)
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continue;
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}
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/* ;;: i think this chunk can replace the below "found end of list" chunk */
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/* otherwise, insert discontinuous node */
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BT_mlistnode *new = calloc(1, sizeof *new);
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new->lo = lob;
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@ -1088,6 +1031,8 @@ _mlist_insert(BT_state *state, void *lo, void *hi)
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return;
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}
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/* TODO: confirm whether this is redundant given discontinuous node insertion
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above */
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/* found end of list */
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BT_mlistnode *new = calloc(1, sizeof *new);
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new->lo = lob;
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@ -1101,7 +1046,7 @@ _nlist_insert2(BT_state *state, BT_nlistnode **dst, BT_page *lo, BT_page *hi)
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{
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BT_nlistnode **prev_dst = 0;
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while(*dst) { /* ;;: this is a problem */
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while(*dst) {
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if (hi == (*dst)->lo) {
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(*dst)->lo = lo;
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/* check if we can coalesce with left neighbor */
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@ -1137,9 +1082,19 @@ _nlist_insert2(BT_state *state, BT_nlistnode **dst, BT_page *lo, BT_page *hi)
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dst = &(*dst)->next;
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continue;
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}
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/* otherwise, insert discontinuous node */
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BT_nlistnode *new = calloc(1, sizeof *new);
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new->lo = lo;
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new->hi = hi;
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new->next = *dst;
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*dst = new;
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return;
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}
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/* otherwise, insert discontinuous node */
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/* TODO: confirm whether this is redundant given discontinuous node insertion
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above */
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/* found end of list */
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BT_nlistnode *new = calloc(1, sizeof *new);
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new->lo = lo;
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new->hi = hi;
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@ -2546,7 +2501,7 @@ _bt_state_load(BT_state *state)
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}
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/* map the node segment */
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_bt_state_map_node_segment(state); /* ;;: this should follow a call to _bt_state_meta_new. hmm... but that leads to a bad dependency graph. We may need to separately initialize the first partition and only call map_node_segment on restore. */
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_bt_state_map_node_segment(state);
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/* new db, so populate metadata */
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if (new) {
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@ -3326,37 +3281,3 @@ _bt_printnode(BT_page *node)
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fprintf(stderr, "[%5zu] %10x %10x\n", i, node->datk[i].va, node->datk[i].fo);
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}
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}
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/*
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re: partition striping, I find the following somewhat confusing.
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A pgno for a node could be either:
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1) Its actual pgno in the persistent file
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2) merely a page offset into the memory arena
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The pgno that a parent node stores for a child need not be (1) if the memory
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maps are properly restored from the blk_base array in the metapage. Right?
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So, on startup:
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before traversing nodes, restore the memory map by mapping each partition
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successively after the other. Do this for all non-zero page offsets in
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blk_base.
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If this is done, then _node_get and _fo_get can remain largely unchanged
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Is there any reason this won't work?
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---------------------------
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If we have to do (2) for some reason. Then _node_get and _fo_get /will/ have
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to read the blk_base array and appropriately translate using the offsets and
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partition sizes.
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is _bt_data_cow a problem?
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*/
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