raid5: add an option to avoid copy data from bio to stripe cache
The stripe cache has two goals: 1. cache data, so next time if data can be found in stripe cache, disk access can be avoided. 2. stable data. data is copied from bio to stripe cache and calculated parity. data written to disk is from stripe cache, so if upper layer changes bio data, data written to disk isn't impacted. In my environment, I can guarantee 2 will not happen. And BDI_CAP_STABLE_WRITES can guarantee 2 too. For 1, it's not common too. block plug mechanism will dispatch a bunch of sequentail small requests together. And since I'm using SSD, I'm using small chunk size. It's rare case stripe cache is really useful. So I'd like to avoid the copy from bio to stripe cache and it's very helpful for performance. In my 1M randwrite tests, avoid the copy can increase the performance more than 30%. Of course, this shouldn't be enabled by default. It's reported enabling BDI_CAP_STABLE_WRITES can harm some workloads before, so I added an option to control it. Neilb: changed BUG_ON to WARN_ON Removed some assignments from raid5_build_block which are now not needed. Signed-off-by: Shaohua Li <shli@fusionio.com> Signed-off-by: NeilBrown <neilb@suse.de>
This commit is contained in:
Shaohua Li
NeilBrown
parent
f2e06c5884
commit
d592a99691
@ -487,6 +487,7 @@ static void shrink_buffers(struct stripe_head *sh)
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int num = sh->raid_conf->pool_size;
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for (i = 0; i < num ; i++) {
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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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continue;
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@ -507,6 +508,7 @@ static int grow_buffers(struct stripe_head *sh)
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return 1;
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}
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sh->dev[i].page = page;
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sh->dev[i].orig_page = page;
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}
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return 0;
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}
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@ -863,6 +865,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
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if (test_bit(R5_ReadNoMerge, &sh->dev[i].flags))
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bi->bi_rw |= REQ_NOMERGE;
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if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
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WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
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sh->dev[i].vec.bv_page = sh->dev[i].page;
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bi->bi_vcnt = 1;
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bi->bi_io_vec[0].bv_len = STRIPE_SIZE;
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bi->bi_io_vec[0].bv_offset = 0;
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@ -907,6 +912,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
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else
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rbi->bi_iter.bi_sector = (sh->sector
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+ rrdev->data_offset);
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if (test_bit(R5_SkipCopy, &sh->dev[i].flags))
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WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
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sh->dev[i].rvec.bv_page = sh->dev[i].page;
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rbi->bi_vcnt = 1;
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rbi->bi_io_vec[0].bv_len = STRIPE_SIZE;
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rbi->bi_io_vec[0].bv_offset = 0;
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@ -935,8 +943,9 @@ static void ops_run_io(struct stripe_head *sh, struct stripe_head_state *s)
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}
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static struct dma_async_tx_descriptor *
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async_copy_data(int frombio, struct bio *bio, struct page *page,
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sector_t sector, struct dma_async_tx_descriptor *tx)
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async_copy_data(int frombio, struct bio *bio, struct page **page,
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sector_t sector, struct dma_async_tx_descriptor *tx,
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struct stripe_head *sh)
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{
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struct bio_vec bvl;
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struct bvec_iter iter;
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@ -973,11 +982,16 @@ async_copy_data(int frombio, struct bio *bio, struct page *page,
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if (clen > 0) {
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b_offset += bvl.bv_offset;
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bio_page = bvl.bv_page;
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if (frombio)
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tx = async_memcpy(page, bio_page, page_offset,
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if (frombio) {
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if (sh->raid_conf->skip_copy &&
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b_offset == 0 && page_offset == 0 &&
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clen == STRIPE_SIZE)
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*page = bio_page;
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else
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tx = async_memcpy(*page, bio_page, page_offset,
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b_offset, clen, &submit);
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else
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tx = async_memcpy(bio_page, page, b_offset,
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} else
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tx = async_memcpy(bio_page, *page, b_offset,
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page_offset, clen, &submit);
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}
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/* chain the operations */
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@ -1053,8 +1067,8 @@ static void ops_run_biofill(struct stripe_head *sh)
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spin_unlock_irq(&sh->stripe_lock);
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while (rbi && rbi->bi_iter.bi_sector <
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dev->sector + STRIPE_SECTORS) {
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tx = async_copy_data(0, rbi, dev->page,
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dev->sector, tx);
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tx = async_copy_data(0, rbi, &dev->page,
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dev->sector, tx, sh);
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rbi = r5_next_bio(rbi, dev->sector);
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}
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}
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@ -1392,6 +1406,7 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
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BUG_ON(dev->written);
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wbi = dev->written = chosen;
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spin_unlock_irq(&sh->stripe_lock);
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WARN_ON(dev->page != dev->orig_page);
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while (wbi && wbi->bi_iter.bi_sector <
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dev->sector + STRIPE_SECTORS) {
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@ -1401,9 +1416,15 @@ ops_run_biodrain(struct stripe_head *sh, struct dma_async_tx_descriptor *tx)
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set_bit(R5_SyncIO, &dev->flags);
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if (wbi->bi_rw & REQ_DISCARD)
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set_bit(R5_Discard, &dev->flags);
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else
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tx = async_copy_data(1, wbi, dev->page,
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dev->sector, tx);
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else {
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tx = async_copy_data(1, wbi, &dev->page,
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dev->sector, tx, sh);
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if (dev->page != dev->orig_page) {
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set_bit(R5_SkipCopy, &dev->flags);
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clear_bit(R5_UPTODATE, &dev->flags);
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clear_bit(R5_OVERWRITE, &dev->flags);
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}
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}
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wbi = r5_next_bio(wbi, dev->sector);
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}
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}
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@ -1434,7 +1455,7 @@ static void ops_complete_reconstruct(void *stripe_head_ref)
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struct r5dev *dev = &sh->dev[i];
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if (dev->written || i == pd_idx || i == qd_idx) {
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if (!discard)
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if (!discard && !test_bit(R5_SkipCopy, &dev->flags))
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set_bit(R5_UPTODATE, &dev->flags);
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if (fua)
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set_bit(R5_WantFUA, &dev->flags);
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@ -1847,8 +1868,10 @@ static int resize_stripes(struct r5conf *conf, int newsize)
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osh = get_free_stripe(conf, hash);
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unlock_device_hash_lock(conf, hash);
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atomic_set(&nsh->count, 1);
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for(i=0; i<conf->pool_size; i++)
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for(i=0; i<conf->pool_size; i++) {
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nsh->dev[i].page = osh->dev[i].page;
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nsh->dev[i].orig_page = osh->dev[i].page;
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}
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for( ; i<newsize; i++)
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nsh->dev[i].page = NULL;
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nsh->hash_lock_index = hash;
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@ -1904,6 +1927,7 @@ static int resize_stripes(struct r5conf *conf, int newsize)
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if (nsh->dev[i].page == NULL) {
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struct page *p = alloc_page(GFP_NOIO);
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nsh->dev[i].page = p;
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nsh->dev[i].orig_page = p;
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if (!p)
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err = -ENOMEM;
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}
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@ -2141,24 +2165,20 @@ static void raid5_end_write_request(struct bio *bi, int error)
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}
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static sector_t compute_blocknr(struct stripe_head *sh, int i, int previous);
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static void raid5_build_block(struct stripe_head *sh, int i, int previous)
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{
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struct r5dev *dev = &sh->dev[i];
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bio_init(&dev->req);
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dev->req.bi_io_vec = &dev->vec;
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dev->req.bi_vcnt++;
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dev->req.bi_max_vecs++;
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dev->req.bi_max_vecs = 1;
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dev->req.bi_private = sh;
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dev->vec.bv_page = dev->page;
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bio_init(&dev->rreq);
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dev->rreq.bi_io_vec = &dev->rvec;
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dev->rreq.bi_vcnt++;
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dev->rreq.bi_max_vecs++;
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dev->rreq.bi_max_vecs = 1;
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dev->rreq.bi_private = sh;
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dev->rvec.bv_page = dev->page;
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dev->flags = 0;
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dev->sector = compute_blocknr(sh, i, previous);
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@ -2758,6 +2778,11 @@ handle_failed_stripe(struct r5conf *conf, struct stripe_head *sh,
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/* and fail all 'written' */
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bi = sh->dev[i].written;
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sh->dev[i].written = NULL;
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if (test_and_clear_bit(R5_SkipCopy, &sh->dev[i].flags)) {
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WARN_ON(test_bit(R5_UPTODATE, &sh->dev[i].flags));
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sh->dev[i].page = sh->dev[i].orig_page;
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}
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if (bi) bitmap_end = 1;
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while (bi && bi->bi_iter.bi_sector <
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sh->dev[i].sector + STRIPE_SECTORS) {
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@ -3002,12 +3027,17 @@ static void handle_stripe_clean_event(struct r5conf *conf,
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dev = &sh->dev[i];
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if (!test_bit(R5_LOCKED, &dev->flags) &&
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(test_bit(R5_UPTODATE, &dev->flags) ||
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test_bit(R5_Discard, &dev->flags))) {
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test_bit(R5_Discard, &dev->flags) ||
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test_bit(R5_SkipCopy, &dev->flags))) {
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/* We can return any write requests */
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struct bio *wbi, *wbi2;
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pr_debug("Return write for disc %d\n", i);
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if (test_and_clear_bit(R5_Discard, &dev->flags))
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clear_bit(R5_UPTODATE, &dev->flags);
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if (test_and_clear_bit(R5_SkipCopy, &dev->flags)) {
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WARN_ON(test_bit(R5_UPTODATE, &dev->flags));
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dev->page = dev->orig_page;
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}
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wbi = dev->written;
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dev->written = NULL;
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while (wbi && wbi->bi_iter.bi_sector <
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@ -3026,6 +3056,8 @@ static void handle_stripe_clean_event(struct r5conf *conf,
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0);
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} else if (test_bit(R5_Discard, &dev->flags))
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discard_pending = 1;
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WARN_ON(test_bit(R5_SkipCopy, &dev->flags));
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WARN_ON(dev->page != dev->orig_page);
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}
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if (!discard_pending &&
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test_bit(R5_Discard, &sh->dev[sh->pd_idx].flags)) {
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@ -5365,6 +5397,50 @@ raid5_preread_bypass_threshold = __ATTR(preread_bypass_threshold,
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raid5_show_preread_threshold,
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raid5_store_preread_threshold);
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static ssize_t
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raid5_show_skip_copy(struct mddev *mddev, char *page)
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{
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struct r5conf *conf = mddev->private;
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if (conf)
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return sprintf(page, "%d\n", conf->skip_copy);
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else
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return 0;
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}
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static ssize_t
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raid5_store_skip_copy(struct mddev *mddev, const char *page, size_t len)
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{
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struct r5conf *conf = mddev->private;
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unsigned long new;
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if (len >= PAGE_SIZE)
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return -EINVAL;
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if (!conf)
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return -ENODEV;
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if (kstrtoul(page, 10, &new))
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return -EINVAL;
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new = !!new;
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if (new == conf->skip_copy)
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return len;
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mddev_suspend(mddev);
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conf->skip_copy = new;
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if (new)
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mddev->queue->backing_dev_info.capabilities |=
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BDI_CAP_STABLE_WRITES;
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else
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mddev->queue->backing_dev_info.capabilities &=
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~BDI_CAP_STABLE_WRITES;
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mddev_resume(mddev);
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return len;
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}
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static struct md_sysfs_entry
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raid5_skip_copy = __ATTR(skip_copy, S_IRUGO | S_IWUSR,
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raid5_show_skip_copy,
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raid5_store_skip_copy);
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static ssize_t
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stripe_cache_active_show(struct mddev *mddev, char *page)
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{
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@ -5450,6 +5526,7 @@ static struct attribute *raid5_attrs[] = {
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&raid5_stripecache_active.attr,
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&raid5_preread_bypass_threshold.attr,
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&raid5_group_thread_cnt.attr,
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&raid5_skip_copy.attr,
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NULL,
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};
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static struct attribute_group raid5_attrs_group = {
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@ -232,7 +232,7 @@ struct stripe_head {
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*/
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struct bio req, rreq;
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struct bio_vec vec, rvec;
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struct page *page;
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struct page *page, *orig_page;
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struct bio *toread, *read, *towrite, *written;
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sector_t sector; /* sector of this page */
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unsigned long flags;
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@ -299,6 +299,7 @@ enum r5dev_flags {
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* data in, and now is a good time to write it out.
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*/
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R5_Discard, /* Discard the stripe */
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R5_SkipCopy, /* Don't copy data from bio to stripe cache */
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};
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/*
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@ -436,6 +437,7 @@ struct r5conf {
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atomic_t pending_full_writes; /* full write backlog */
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int bypass_count; /* bypassed prereads */
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int bypass_threshold; /* preread nice */
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int skip_copy; /* Don't copy data from bio to stripe cache */
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struct list_head *last_hold; /* detect hold_list promotions */
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atomic_t reshape_stripes; /* stripes with pending writes for reshape */
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