Describe the rationale for the decisions a bit better.
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
fs/xfs/xfs_zone_alloc.c | 15 +++++++++------
1 file changed, 9 insertions(+), 6 deletions(-)
diff --git a/fs/xfs/xfs_zone_alloc.c b/fs/xfs/xfs_zone_alloc.c
index d9e2b1411434..c1f053f4a82a 100644
--- a/fs/xfs/xfs_zone_alloc.c
+++ b/fs/xfs/xfs_zone_alloc.c
@@ -1114,24 +1114,27 @@ xfs_get_zone_info_cb(
}
/*
- * Calculate the max open zone limit based on the of number of
- * backing zones available
+ * Calculate the max open zone limit based on the of number of backing zones
+ * available.
*/
static inline uint32_t
xfs_max_open_zones(
struct xfs_mount *mp)
{
unsigned int max_open, max_open_data_zones;
+
/*
- * We need two zones for every open data zone,
- * one in reserve as we don't reclaim open zones. One data zone
- * and its spare is included in XFS_MIN_ZONES.
+ * We need two zones for every open data zone, one in reserve as we
+ * don't reclaim open zones. One data zone and its spare is included
+ * in XFS_MIN_ZONES to support at least one user data writer.
*/
max_open_data_zones = (mp->m_sb.sb_rgcount - XFS_MIN_ZONES) / 2 + 1;
max_open = max_open_data_zones + XFS_OPEN_GC_ZONES;
/*
- * Cap the max open limit to 1/4 of available space
+ * Cap the max open limit to 1/4 of available space. Without this we'd
+ * run out of easy reclaim targets too quickly and storage devices don't
+ * handle huge numbers of concurrent write streams overly well.
*/
return clamp(max_open, XFS_MIN_OPEN_ZONES, mp->m_sb.sb_rgcount / 4);
}
--
2.47.2
