mirror of
https://git.proxmox.com/git/mirror_zfs.git
synced 2024-12-28 03:49:38 +03:00
f8c0d7e1f6
`__vdev_disk_physio()` uses `abd_nr_pages_off()` to allocate a bio with a sufficient number of iovec's to process this zio (i.e. `nr_iovecs`/`bi_max_vecs`). If there are not enough iovec's in the bio, then additional bio's will be allocated. However, this is a sub-optimal code path. In particular, it requires several abd calls (to `abd_nr_pages_off()` and `abd_bio_map_off()`) which will have to walk the constituents of the ABD (the pages or the gang children) because they are looking for offsets > 0. For gang ABD's, `abd_nr_pages_off()` returns the number of iovec's needed for the first constituent, rather than the sum of all constituents (within the requested range). This always under-estimates the required number of iovec's, which causes us to always need several bio's. The end result is that `__vdev_disk_physio()` is usually O(n^2) for gang ABD's (and occasionally O(n^3), when more than 16 bio's are needed). This commit fixes `abd_nr_pages_off()`'s handling of gang ABD's, to correctly determine how many iovec's are needed, by adding up the number of iovec's for each of the gang children in the requested range. Reviewed-by: Mark Maybee <mark.maybee@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Reviewed-by: Brian Atkinson <batkinson@lanl.gov> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> Closes #11536 |
||
|---|---|---|
| .. | ||
| abd_os.c | ||
| arc_os.c | ||
| Makefile.in | ||
| mmp_os.c | ||
| policy.c | ||
| qat_compress.c | ||
| qat_crypt.c | ||
| qat.c | ||
| spa_misc_os.c | ||
| trace.c | ||
| vdev_disk.c | ||
| vdev_file.c | ||
| zfs_acl.c | ||
| zfs_ctldir.c | ||
| zfs_debug.c | ||
| zfs_dir.c | ||
| zfs_file_os.c | ||
| zfs_ioctl_os.c | ||
| zfs_sysfs.c | ||
| zfs_uio.c | ||
| zfs_vfsops.c | ||
| zfs_vnops_os.c | ||
| zfs_znode.c | ||
| zio_crypt.c | ||
| zpl_ctldir.c | ||
| zpl_export.c | ||
| zpl_file.c | ||
| zpl_inode.c | ||
| zpl_super.c | ||
| zpl_xattr.c | ||
| zvol_os.c | ||