From e639fe97eabe40445ad6c1308125ce8c2687ec6f Mon Sep 17 00:00:00 2001
From: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
Date: Thu, 7 Apr 2022 16:40:37 -0300
Subject: [PATCH] Increase the value for max_vas_reuse_count
 
While running tests on PowerVM with 1MB files, it has been noticed a
huge delay when processing the 100th stream.
The penalty for reopening the VAS window is still too high for 100
executions and is being increased to 10000 in order to keep its execution less
than 10% of the time spent executing those 10000 streams.
 
Signed-off-by: Tulio Magno Quites Machado Filho <tuliom@linux.ibm.com>
---
 lib/nx_zlib.c     | 13 ++++++++++++-
 test/nx-zlib.conf |  4 ++--
 2 files changed, 14 insertions(+), 3 deletions(-)
 
diff --git a/lib/nx_zlib.c b/lib/nx_zlib.c
index fa7000e..b3737a2 100644
--- a/lib/nx_zlib.c
+++ b/lib/nx_zlib.c
@@ -982,7 +982,18 @@ void nx_hw_init(void)
 	nx_config.max_byte_count_current = (1UL<<30);
 	nx_config.max_source_dde_count = MAX_DDE_COUNT;
 	nx_config.max_target_dde_count = MAX_DDE_COUNT;
-	nx_config.max_vas_reuse_count = 100;
+	/** On PowerVM, reopening a VAS window takes 300x the time used to
+	 *  process a single stream with the maximum per job length allowed,
+	 *  causing serious performance issues when max_vas_reuse_count is too
+	 *  low. In order to avoid these issues, it has been decided the
+	 *  average impact of reopening a VAS window should be less than 10% of
+	 *  of the time spent processing max_vas_reuse_count streams at
+	 *  maximum per job length.  That means 3000, which we rounded up.
+	 *  Notice that setting this number too high may impact the performance
+	 *  of multithreaded processes with a massive amount of threads. For
+	 *  those cases, it's recommended to use a lower value in the config
+	 *  file. */
+	nx_config.max_vas_reuse_count = 10000;
 	nx_config.per_job_len = nx_query_job_limits(); /* less than suspend limit */
 	nx_config.strm_def_bufsz = (1024 * 1024); /* affect the deflate fifo_out */
 	nx_config.soft_copy_threshold = 1024; /* choose memcpy or hwcopy */
diff --git a/test/nx-zlib.conf b/test/nx-zlib.conf
index 444d966..cb30c36 100644
--- a/test/nx-zlib.conf
+++ b/test/nx-zlib.conf
@@ -59,5 +59,5 @@ logfile = ./nx.log
 #nx_ratio_s = 100
 
 # Maximum number of times deflateInit/inflateInit can reuse an already-open VAS
-# window
-# max_vas_reuse_count = 100
+# window. Default: 10000
+# max_vas_reuse_count = 10000