On Wed, Jun 07, 2017 at 06:09:33PM +0000, Sargun Dhillon wrote: > This patch is a small performance optimization to get rid of a spin > lock, where instead an atomic64_t can be used. > > Signed-off-by: Sargun Dhillon <sar...@sargun.me> [snip] > diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c > index 017b67d..0123974 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -2417,9 +2417,7 @@ int btrfs_init_new_device(struct btrfs_fs_info > *fs_info, const char *device_path > fs_info->fs_devices->total_devices++; > fs_info->fs_devices->total_rw_bytes += device->total_bytes; > > - spin_lock(&fs_info->free_chunk_lock); > - fs_info->free_chunk_space += device->total_bytes; > - spin_unlock(&fs_info->free_chunk_lock); > + atomic64_add(device->total_bytes, &fs_info->free_chunk_space); > > if (!blk_queue_nonrot(q)) > fs_info->fs_devices->rotating = 1; > @@ -2874,9 +2872,7 @@ int btrfs_remove_chunk(struct btrfs_trans_handle *trans, > mutex_lock(&fs_info->chunk_mutex); > btrfs_device_set_bytes_used(device, > device->bytes_used - dev_extent_len); > - spin_lock(&fs_info->free_chunk_lock); > - fs_info->free_chunk_space += dev_extent_len; > - spin_unlock(&fs_info->free_chunk_lock); > + atomic64_add(dev_extent_len, > &fs_info->free_chunk_space); > btrfs_clear_space_info_full(fs_info); > mutex_unlock(&fs_info->chunk_mutex); > } > @@ -4409,9 +4405,7 @@ int btrfs_shrink_device(struct btrfs_device *device, > u64 new_size) > btrfs_device_set_total_bytes(device, new_size); > if (device->writeable) { > device->fs_devices->total_rw_bytes -= diff; > - spin_lock(&fs_info->free_chunk_lock); > - fs_info->free_chunk_space -= diff; > - spin_unlock(&fs_info->free_chunk_lock); > + atomic64_sub(diff, &fs_info->free_chunk_space); > } > mutex_unlock(&fs_info->chunk_mutex); > > @@ -4535,9 +4529,7 @@ int btrfs_shrink_device(struct btrfs_device *device, > u64 new_size) > btrfs_device_set_total_bytes(device, old_size); > if (device->writeable) > device->fs_devices->total_rw_bytes += diff; > - spin_lock(&fs_info->free_chunk_lock); > - fs_info->free_chunk_space += diff; > - spin_unlock(&fs_info->free_chunk_lock); > + atomic64_add(diff, &fs_info->free_chunk_space); > mutex_unlock(&fs_info->chunk_mutex); > } > return ret; > @@ -4882,9 +4874,7 @@ static int __btrfs_alloc_chunk(struct > btrfs_trans_handle *trans, > btrfs_device_set_bytes_used(map->stripes[i].dev, num_bytes); > } > > - spin_lock(&info->free_chunk_lock); > - info->free_chunk_space -= (stripe_size * map->num_stripes); > - spin_unlock(&info->free_chunk_lock); > + atomic64_sub((stripe_size * map->num_stripes), &info->free_chunk_space);
Can you please get rid of the extra parentheses around the multiplication here? Also curious if you were able to measure any sort of performance difference. Besides that, Reviewed-by: Omar Sandoval <osan...@fb.com> > > free_extent_map(em); > check_raid56_incompat_flag(info, type); > @@ -6684,10 +6674,8 @@ static int read_one_dev(struct btrfs_fs_info *fs_info, > device->in_fs_metadata = 1; > if (device->writeable && !device->is_tgtdev_for_dev_replace) { > device->fs_devices->total_rw_bytes += device->total_bytes; > - spin_lock(&fs_info->free_chunk_lock); > - fs_info->free_chunk_space += device->total_bytes - > - device->bytes_used; > - spin_unlock(&fs_info->free_chunk_lock); > + atomic64_add(device->total_bytes - device->bytes_used, > + &fs_info->free_chunk_space); > } > ret = 0; > return ret; > -- > 2.9.3 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majord...@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html