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