md/raid5: let multiple devices of stripe_head share page
In current implementation, grow_buffers() uses alloc_page() to
allocate the buffers for each stripe_head, i.e. allocate a page
for each dev[i] in stripe_head.
After setting stripe_size as a configurable value by writing
sysfs entry, it means that we always allocate 64K buffers, but
just use 4K of them when stripe_size is 4K in 64KB arm64.
To avoid wasting memory, we try to let multiple sh->dev share
one real page. That means, multiple sh->dev[i].page will point
to the only page with different offset. Example of 64K PAGE_SIZE
and 4K stripe_size as following:
64K PAGE_SIZE
+---+---+---+---+------------------------------+
| | | | |
| | | | |
+-+-+-+-+-+-+-+-+------------------------------+
^ ^ ^ ^
| | | +----------------------------+
| | | |
| | +-------------------+ |
| | | |
| +----------+ | |
| | | |
+-+ | | |
| | | |
+-----+-----+------+-----+------+-----+------+------+
sh | offset(0) | offset(4K) | offset(8K) | offset(12K) |
+ +-----------+------------+------------+-------------+
+----> dev[0].page dev[1].page dev[2].page dev[3].page
A new 'pages' array will be added into stripe_head to record shared
page used by this stripe_head. Allocate them when grow_buffers()
and free them when shrink_buffers().
After trying to share page, the users of sh->dev[i].page need to take
care of the related page offset: page of issued bio and page passed
to xor compution functions. But thanks for previous different page offset
supported. Here, we just need to set correct dev[i].offset.
Signed-off-by: Yufen Yu <yuyufen@huawei.com>
Signed-off-by: Song Liu <songliubraving@fb.com>
This commit is contained in:
Yufen Yu
Song Liu
parent
4f86ff5580
commit
046169f048
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@ -448,13 +448,74 @@ static struct stripe_head *get_free_stripe(struct r5conf *conf, int hash)
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return sh;
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}
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#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
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static void free_stripe_pages(struct stripe_head *sh)
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{
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int i;
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struct page *p;
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/* Have not allocate page pool */
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if (!sh->pages)
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return;
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for (i = 0; i < sh->nr_pages; i++) {
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p = sh->pages[i];
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if (p)
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put_page(p);
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sh->pages[i] = NULL;
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}
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}
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static int alloc_stripe_pages(struct stripe_head *sh, gfp_t gfp)
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{
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int i;
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struct page *p;
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for (i = 0; i < sh->nr_pages; i++) {
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/* The page have allocated. */
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if (sh->pages[i])
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continue;
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p = alloc_page(gfp);
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if (!p) {
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free_stripe_pages(sh);
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return -ENOMEM;
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}
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sh->pages[i] = p;
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}
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return 0;
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}
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static int
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init_stripe_shared_pages(struct stripe_head *sh, struct r5conf *conf, int disks)
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{
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int nr_pages, cnt;
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if (sh->pages)
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return 0;
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/* Each of the sh->dev[i] need one conf->stripe_size */
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cnt = PAGE_SIZE / conf->stripe_size;
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nr_pages = (disks + cnt - 1) / cnt;
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sh->pages = kcalloc(nr_pages, sizeof(struct page *), GFP_KERNEL);
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if (!sh->pages)
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return -ENOMEM;
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sh->nr_pages = nr_pages;
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sh->stripes_per_page = cnt;
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return 0;
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}
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#endif
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static void shrink_buffers(struct stripe_head *sh)
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{
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struct page *p;
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int i;
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int num = sh->raid_conf->pool_size;
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#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
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for (i = 0; i < num ; i++) {
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struct page *p;
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WARN_ON(sh->dev[i].page != sh->dev[i].orig_page);
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p = sh->dev[i].page;
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if (!p)
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@ -462,6 +523,11 @@ static void shrink_buffers(struct stripe_head *sh)
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sh->dev[i].page = NULL;
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put_page(p);
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}
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#else
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for (i = 0; i < num; i++)
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sh->dev[i].page = NULL;
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free_stripe_pages(sh); /* Free pages */
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#endif
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}
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static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
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@ -469,6 +535,7 @@ static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
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int i;
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int num = sh->raid_conf->pool_size;
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#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
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for (i = 0; i < num; i++) {
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struct page *page;
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@ -479,7 +546,16 @@ static int grow_buffers(struct stripe_head *sh, gfp_t gfp)
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sh->dev[i].orig_page = page;
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sh->dev[i].offset = 0;
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}
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#else
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if (alloc_stripe_pages(sh, gfp))
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return -ENOMEM;
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for (i = 0; i < num; i++) {
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sh->dev[i].page = raid5_get_dev_page(sh, i);
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sh->dev[i].orig_page = sh->dev[i].page;
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sh->dev[i].offset = raid5_get_page_offset(sh, i);
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}
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#endif
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return 0;
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}
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@ -2205,6 +2281,9 @@ static void raid_run_ops(struct stripe_head *sh, unsigned long ops_request)
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static void free_stripe(struct kmem_cache *sc, struct stripe_head *sh)
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{
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#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
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kfree(sh->pages);
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#endif
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if (sh->ppl_page)
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__free_page(sh->ppl_page);
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kmem_cache_free(sc, sh);
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@ -2238,9 +2317,15 @@ static struct stripe_head *alloc_stripe(struct kmem_cache *sc, gfp_t gfp,
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sh->ppl_page = alloc_page(gfp);
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if (!sh->ppl_page) {
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free_stripe(sc, sh);
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sh = NULL;
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return NULL;
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}
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}
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#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
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if (init_stripe_shared_pages(sh, conf, disks)) {
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free_stripe(sc, sh);
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return NULL;
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}
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#endif
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}
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return sh;
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}
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@ -195,6 +195,7 @@ enum reconstruct_states {
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reconstruct_state_result,
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};
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#define DEFAULT_STRIPE_SIZE 4096
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struct stripe_head {
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struct hlist_node hash;
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struct list_head lru; /* inactive_list or handle_list */
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@ -246,6 +247,13 @@ struct stripe_head {
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int target, target2;
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enum sum_check_flags zero_sum_result;
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} ops;
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#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
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/* These pages will be used by bios in dev[i] */
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struct page **pages;
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int nr_pages; /* page array size */
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int stripes_per_page;
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#endif
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struct r5dev {
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/* rreq and rvec are used for the replacement device when
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* writing data to both devices.
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@ -473,7 +481,6 @@ struct disk_info {
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*/
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#define NR_STRIPES 256
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#define DEFAULT_STRIPE_SIZE 4096
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#if PAGE_SIZE == DEFAULT_STRIPE_SIZE
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#define STRIPE_SIZE PAGE_SIZE
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@ -772,6 +779,25 @@ static inline int algorithm_is_DDF(int layout)
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return layout >= 8 && layout <= 10;
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}
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#if PAGE_SIZE != DEFAULT_STRIPE_SIZE
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/*
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* Return offset of the corresponding page for r5dev.
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*/
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static inline int raid5_get_page_offset(struct stripe_head *sh, int disk_idx)
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{
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return (disk_idx % sh->stripes_per_page) * RAID5_STRIPE_SIZE(sh->raid_conf);
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}
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/*
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* Return corresponding page address for r5dev.
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*/
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static inline struct page *
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raid5_get_dev_page(struct stripe_head *sh, int disk_idx)
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{
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return sh->pages[disk_idx / sh->stripes_per_page];
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}
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#endif
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extern void md_raid5_kick_device(struct r5conf *conf);
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extern int raid5_set_cache_size(struct mddev *mddev, int size);
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extern sector_t raid5_compute_blocknr(struct stripe_head *sh, int i, int previous);
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