From 387834bae9bd9fac26fccadde85328f9db730be0 Mon Sep 17 00:00:00 2001
From: Radoslaw Zarzynski <rzarzyns@redhat.com>
Date: Mon, 1 Feb 2021 14:59:49 +0100
Subject: [PATCH] crimson: make the number of alien threads configurable.

It's particularly important for reads to have large-enough
thread pool in `AlienStore` as they are synchronous; that
is, e.g. `BlueStore` blocks on IO when handling reads.

This commit introduces a configurable allowing operators
to increase the number from `1` which we were limited to
before the change.

Naming similarity with `osd_op_num_threads_per_shard` is
intentional.

Signed-off-by: Radoslaw Zarzynski <rzarzyns@redhat.com>
---
 src/common/options.cc                    | 5 +++++
 src/crimson/os/alienstore/alien_store.cc | 4 +++-
 2 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/common/options.cc b/src/common/options.cc
index 2cfe188a8f64f..e8cbcf2ab8e63 100644
--- a/src/common/options.cc
+++ b/src/common/options.cc
@@ -5519,6 +5519,11 @@ std::vector<Option> get_global_options() {
     .set_default(0)
     .set_description("The maximum number concurrent IO operations, 0 for unlimited"),
 
+    Option("crimson_alien_op_num_threads", Option::TYPE_UINT, Option::LEVEL_ADVANCED)
+    .set_default(16)
+    .set_flag(Option::FLAG_STARTUP)
+    .set_description("The number of threads for serving alienized ObjectStore"),
+
     // ----------------------------
     // blk specific options
     Option("bdev_type", Option::TYPE_STR, Option::LEVEL_ADVANCED)
diff --git a/src/crimson/os/alienstore/alien_store.cc b/src/crimson/os/alienstore/alien_store.cc
index cb55532545b47..8b4e666b3f68d 100644
--- a/src/crimson/os/alienstore/alien_store.cc
+++ b/src/crimson/os/alienstore/alien_store.cc
@@ -71,7 +71,9 @@ AlienStore::AlienStore(const std::string& path, const ConfigValues& values)
     logger().error("{}: unable to get nproc: {}", __func__, errno);
     cpu_id = -1;
   }
-  tp = std::make_unique<crimson::os::ThreadPool>(1, 128, cpu_id);
+  const auto num_threads =
+    cct->_conf.get_val<uint64_t>("crimson_alien_op_num_threads");
+  tp = std::make_unique<crimson::os::ThreadPool>(num_threads, 128, cpu_id);
 }
 
 seastar::future<> AlienStore::start()
-- 
2.39.5