From 920f325d039c053bddd7ddbac3ed55f151b6d2a1 Mon Sep 17 00:00:00 2001
From: Lin Huang <lin.huang@eosnetwork.com>
Date: Fri, 8 Sep 2023 11:02:30 -0400
Subject: [PATCH] Add comments explaining why max supported number of read-only
 threads can be increased

---
 plugins/producer_plugin/producer_plugin.cpp | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/plugins/producer_plugin/producer_plugin.cpp b/plugins/producer_plugin/producer_plugin.cpp
index dbebf6dff6..bffdf69e4d 100644
--- a/plugins/producer_plugin/producer_plugin.cpp
+++ b/plugins/producer_plugin/producer_plugin.cpp
@@ -617,6 +617,12 @@ class producer_plugin_impl : public std::enable_shared_from_this<producer_plugin
    };
 
    uint32_t _ro_thread_pool_size{0};
+   // In EOS VM OC tierup, 10 pages (11 slices) virtual memory is reserved for
+   // each read-only thread and 528 pages (529 slices) for the main-thread memory.
+   // With maximum 128 read-only threads, virtual memory required by OC is
+   // 15TB (OC's main thread uses 4TB VM (by 529 slices) and the read-only
+   // threads use 11TB (128 * 11 * 8GB)). It is about 11.7% of total VM space
+   // in a 64-bit Linux machine (about 128TB).
    static constexpr uint32_t         _ro_max_threads_allowed{128};
    named_thread_pool<struct read>    _ro_thread_pool;
    fc::microseconds                  _ro_write_window_time_us{200000};