6281 prefetching should apply to 1MB reads
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Reviewed by: Alexander Motin <mav@freebsd.org>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Reviewed by: Justin Gibbs <gibbs@scsiguy.com>
Reviewed by: Xin Li <delphij@freebsd.org>
Approved by: Gordon Ross <gordon.ross@nexenta.com>
5987 zfs prefetch code needs work
Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Paul Dagnelie <pcd@delphix.com>
Approved by: Gordon Ross <gordon.ross@nexenta.com>
NEX-4582 update wrc test cases for allow to use write back cache per tree of datasets
Reviewed by: Steve Peng <steve.peng@nexenta.com>
Reviewed by: Alex Aizman <alex.aizman@nexenta.com>
5960 zfs recv should prefetch indirect blocks
5925 zfs receive -o origin=
Reviewed by: Prakash Surya <prakash.surya@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>

*** 209,271 ****
          zstream_t *zs;
          int64_t pf_start, ipf_start, ipf_istart, ipf_iend;
          int64_t pf_ahead_blks, max_blks;
          int epbs, max_dist_blks, pf_nblks, ipf_nblks;
          uint64_t end_of_access_blkid = blkid + nblks;
-         spa_t *spa = zf->zf_dnode->dn_objset->os_spa;
  
          if (zfs_prefetch_disable)
                  return;
  
          /*
-          * If we haven't yet loaded the indirect vdevs' mappings, we
-          * can only read from blocks that we carefully ensure are on
-          * concrete vdevs (or previously-loaded indirect vdevs).  So we
-          * can't allow the predictive prefetcher to attempt reads of other
-          * blocks (e.g. of the MOS's dnode obejct).
-          */
-         if (!spa_indirect_vdevs_loaded(spa))
-                 return;
- 
-         /*
           * As a fast path for small (single-block) files, ignore access
           * to the first block.
           */
          if (blkid == 0)
                  return;
  
          rw_enter(&zf->zf_rwlock, RW_READER);
  
-         /*
-          * Find matching prefetch stream.  Depending on whether the accesses
-          * are block-aligned, first block of the new access may either follow
-          * the last block of the previous access, or be equal to it.
-          */
          for (zs = list_head(&zf->zf_stream); zs != NULL;
              zs = list_next(&zf->zf_stream, zs)) {
!                 if (blkid == zs->zs_blkid || blkid + 1 == zs->zs_blkid) {
                          mutex_enter(&zs->zs_lock);
                          /*
                           * zs_blkid could have changed before we
                           * acquired zs_lock; re-check them here.
                           */
!                         if (blkid == zs->zs_blkid) {
!                                 break;
!                         } else if (blkid + 1 == zs->zs_blkid) {
!                                 blkid++;
!                                 nblks--;
!                                 if (nblks == 0) {
!                                         /* Already prefetched this before. */
                                          mutex_exit(&zs->zs_lock);
!                                         rw_exit(&zf->zf_rwlock);
!                                         return;
                                  }
                                  break;
                          }
-                         mutex_exit(&zs->zs_lock);
                  }
-         }
  
          if (zs == NULL) {
                  /*
                   * This access is not part of any existing stream.  Create
                   * a new stream for it.
--- 209,246 ----
          zstream_t *zs;
          int64_t pf_start, ipf_start, ipf_istart, ipf_iend;
          int64_t pf_ahead_blks, max_blks;
          int epbs, max_dist_blks, pf_nblks, ipf_nblks;
          uint64_t end_of_access_blkid = blkid + nblks;
  
          if (zfs_prefetch_disable)
                  return;
  
          /*
           * As a fast path for small (single-block) files, ignore access
           * to the first block.
           */
          if (blkid == 0)
                  return;
  
          rw_enter(&zf->zf_rwlock, RW_READER);
  
          for (zs = list_head(&zf->zf_stream); zs != NULL;
              zs = list_next(&zf->zf_stream, zs)) {
!                 if (blkid == zs->zs_blkid) {
                          mutex_enter(&zs->zs_lock);
                          /*
                           * zs_blkid could have changed before we
                           * acquired zs_lock; re-check them here.
                           */
!                         if (blkid != zs->zs_blkid) {
                                  mutex_exit(&zs->zs_lock);
!                                 continue;
                          }
                          break;
                  }
          }
  
          if (zs == NULL) {
                  /*
                   * This access is not part of any existing stream.  Create
                   * a new stream for it.