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Pre-load and sort random blocks for pure read verify workloads
If fio is run with a write phase before a read phase and the IO type is random, the end read verify phase will get sorted blocks to read back. But if fio is asked to verify something that was previously randomly written, it will generate the same random offsets in random order and verify those. This is usually much slower than a sorted read back. So add a verifysort_nr option that allows the user to specify a number of random offsets to pre-generate and sort, before reading them and verifying the contents. This greatly speeds up pure read verify workloads. Default to 1024, and put a max of 64K entries on the option. We do a merge list sort on the entries, so we don't want a huge amount of backlog. Signed-off-by: Jens Axboe <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,140 @@ | ||
| #include <stdio.h> | ||
| #include <string.h> | ||
| #include "../flist.h" | ||
| #include "../log.h" | ||
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| #define MAX_LIST_LENGTH_BITS 20 | ||
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| /* | ||
| * Returns a list organized in an intermediate format suited | ||
| * to chaining of merge() calls: null-terminated, no reserved or | ||
| * sentinel head node, "prev" links not maintained. | ||
| */ | ||
| static struct flist_head *merge(void *priv, | ||
| int (*cmp)(void *priv, struct flist_head *a, | ||
| struct flist_head *b), | ||
| struct flist_head *a, struct flist_head *b) | ||
| { | ||
| struct flist_head head, *tail = &head; | ||
|
|
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| while (a && b) { | ||
| /* if equal, take 'a' -- important for sort stability */ | ||
| if ((*cmp)(priv, a, b) <= 0) { | ||
| tail->next = a; | ||
| a = a->next; | ||
| } else { | ||
| tail->next = b; | ||
| b = b->next; | ||
| } | ||
| tail = tail->next; | ||
| } | ||
| tail->next = a?:b; | ||
| return head.next; | ||
| } | ||
|
|
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| /* | ||
| * Combine final list merge with restoration of standard doubly-linked | ||
| * list structure. This approach duplicates code from merge(), but | ||
| * runs faster than the tidier alternatives of either a separate final | ||
| * prev-link restoration pass, or maintaining the prev links | ||
| * throughout. | ||
| */ | ||
| static void merge_and_restore_back_links(void *priv, | ||
| int (*cmp)(void *priv, struct flist_head *a, | ||
| struct flist_head *b), | ||
| struct flist_head *head, | ||
| struct flist_head *a, struct flist_head *b) | ||
| { | ||
| struct flist_head *tail = head; | ||
|
|
||
| while (a && b) { | ||
| /* if equal, take 'a' -- important for sort stability */ | ||
| if ((*cmp)(priv, a, b) <= 0) { | ||
| tail->next = a; | ||
| a->prev = tail; | ||
| a = a->next; | ||
| } else { | ||
| tail->next = b; | ||
| b->prev = tail; | ||
| b = b->next; | ||
| } | ||
| tail = tail->next; | ||
| } | ||
| tail->next = a ? : b; | ||
|
|
||
| do { | ||
| /* | ||
| * In worst cases this loop may run many iterations. | ||
| * Continue callbacks to the client even though no | ||
| * element comparison is needed, so the client's cmp() | ||
| * routine can invoke cond_resched() periodically. | ||
| */ | ||
| (*cmp)(priv, tail->next, tail->next); | ||
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| tail->next->prev = tail; | ||
| tail = tail->next; | ||
| } while (tail->next); | ||
|
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| tail->next = head; | ||
| head->prev = tail; | ||
| } | ||
|
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| /** | ||
| * list_sort - sort a list | ||
| * @priv: private data, opaque to list_sort(), passed to @cmp | ||
| * @head: the list to sort | ||
| * @cmp: the elements comparison function | ||
| * | ||
| * This function implements "merge sort", which has O(nlog(n)) | ||
| * complexity. | ||
| * | ||
| * The comparison function @cmp must return a negative value if @a | ||
| * should sort before @b, and a positive value if @a should sort after | ||
| * @b. If @a and @b are equivalent, and their original relative | ||
| * ordering is to be preserved, @cmp must return 0. | ||
| */ | ||
| void flist_sort(void *priv, struct flist_head *head, | ||
| int (*cmp)(void *priv, struct flist_head *a, | ||
| struct flist_head *b)) | ||
| { | ||
| struct flist_head *part[MAX_LIST_LENGTH_BITS+1]; /* sorted partial lists | ||
| -- last slot is a sentinel */ | ||
| int lev; /* index into part[] */ | ||
| int max_lev = 0; | ||
| struct flist_head *list; | ||
|
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| if (flist_empty(head)) | ||
| return; | ||
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| memset(part, 0, sizeof(part)); | ||
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| head->prev->next = NULL; | ||
| list = head->next; | ||
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| while (list) { | ||
| struct flist_head *cur = list; | ||
| list = list->next; | ||
| cur->next = NULL; | ||
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| for (lev = 0; part[lev]; lev++) { | ||
| cur = merge(priv, cmp, part[lev], cur); | ||
| part[lev] = NULL; | ||
| } | ||
| if (lev > max_lev) { | ||
| if (lev >= MAX_LIST_LENGTH_BITS) { | ||
| log_err("fio: list passed to" | ||
| " list_sort() too long for" | ||
| " efficiency\n"); | ||
| lev--; | ||
| } | ||
| max_lev = lev; | ||
| } | ||
| part[lev] = cur; | ||
| } | ||
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| for (lev = 0; lev < max_lev; lev++) | ||
| if (part[lev]) | ||
| list = merge(priv, cmp, part[lev], list); | ||
|
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| merge_and_restore_back_links(priv, cmp, head, part[max_lev], list); | ||
| } |
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