[PATCH v2 proxmox 1/3] pbs-api-types: add gc chunk metadata prefetch tuning options

[Enrico Plantulli <plantulli@gmail.com>]

Add an opt-in option to defer and batch chunk access time updates in
garbage collection phase 1, plus a separate option for the batch size
to ease benchmarking on different storage backends.

Batched updates are flushed sorted by digest, so the chunk directories
involved can be warmed via readdir right before their chunks are
touched. Keeping the switch opt-in follows the review of the first
version of this series: storage backends that do not prefetch inode
metadata on readdir, such as some network attached storages, may see
no benefit or a regression.

Signed-off-by: Enrico Plantulli <plantulli@gmail.com>
---
 pbs-api-types/src/datastore.rs | 24 ++++++++++++++++++++++++
 1 file changed, 24 insertions(+)

diff --git a/pbs-api-types/src/datastore.rs b/pbs-api-types/src/datastore.rs
index 93ccaf0..79ccff9 100644
--- a/pbs-api-types/src/datastore.rs
+++ b/pbs-api-types/src/datastore.rs
@@ -256,6 +256,14 @@ pub const GC_CACHE_CAPACITY_SCHEMA: Schema =
         .default(1024 * 1024)
         .schema();
 
+pub const GC_PREFETCH_BATCH_SIZE_SCHEMA: Schema = IntegerSchema::new(
+    "Batch size for deferred chunk access time updates in garbage collection phase 1",
+)
+.minimum(1024)
+.maximum(16 * 1024 * 1024)
+.default(1024 * 1024)
+.schema();
+
 #[api(
     properties: {
         "chunk-order": {
@@ -278,6 +286,18 @@ pub const GC_CACHE_CAPACITY_SCHEMA: Schema =
             schema: GC_CACHE_CAPACITY_SCHEMA,
             optional: true,
         },
+        "gc-chunk-metadata-prefetch": {
+            description:
+                "Defer and batch chunk access time updates in garbage collection phase 1, \
+                warming each chunk directory via readdir right before its chunks are touched",
+            optional: true,
+            default: false,
+            type: bool,
+        },
+        "gc-prefetch-batch-size": {
+            schema: GC_PREFETCH_BATCH_SIZE_SCHEMA,
+            optional: true,
+        },
         "default-verification-workers": {
             schema: VERIFY_JOB_VERIFY_THREADS_SCHEMA,
             optional: true,
@@ -304,6 +324,10 @@ pub struct DatastoreTuning {
     #[serde(skip_serializing_if = "Option::is_none")]
     pub gc_cache_capacity: Option<usize>,
     #[serde(skip_serializing_if = "Option::is_none")]
+    pub gc_chunk_metadata_prefetch: Option<bool>,
+    #[serde(skip_serializing_if = "Option::is_none")]
+    pub gc_prefetch_batch_size: Option<usize>,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub default_verification_workers: Option<usize>,
     #[serde(skip_serializing_if = "Option::is_none")]
     pub default_verification_readers: Option<usize>,

base-commit: e3e3ff11b9b92fe1ace89b84c1e15c150e2db660
-- 
2.47.3