linux/debian/patches/patchset-zen/sauce/0020-ZEN-INTERACTIVE-dm-crypt-Disable-workqueues-for-cryp.patch

From be57a2710aef65116767d26930dd1251ff6e060f Mon Sep 17 00:00:00 2001
From: Steven Barrett <steven@liquorix.net>
Date: Sat, 21 May 2022 15:15:09 -0500
Subject: ZEN: INTERACTIVE: dm-crypt: Disable workqueues for crypto ops

Queueing in dm-crypt for crypto operations reduces performance on modern
systems.  As discussed in an article from Cloudflare, they discovered
that queuing was introduced because the crypto subsystem used to be
synchronous.  Since it's now asynchronous, we get double queueing when
using the subsystem through dm-crypt.  This is obviously undesirable and
reduces throughput and increases latency.

Disable queueing when using our Zen Interactive configuration.

Fixes: https://github.com/zen-kernel/zen-kernel/issues/282
---
 drivers/md/dm-crypt.c | 5 +++++
 init/Kconfig          | 1 +
 2 files changed, 6 insertions(+)

--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -3315,6 +3315,11 @@ static int crypt_ctr(struct dm_target *t
 			goto bad;
 	}
 
+#ifdef CONFIG_ZEN_INTERACTIVE
+	set_bit(DM_CRYPT_NO_READ_WORKQUEUE, &cc->flags);
+	set_bit(DM_CRYPT_NO_WRITE_WORKQUEUE, &cc->flags);
+#endif
+
 	ret = crypt_ctr_cipher(ti, argv[0], argv[1]);
 	if (ret < 0)
 		goto bad;
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -164,6 +164,7 @@ config ZEN_INTERACTIVE
 
 	    Default scheduler for SQ..: mq-deadline ->   bfq
 	    Default scheduler for MQ..:        none ->   kyber
+	    DM-Crypt workqueues.......:        yes  ->   no
 
 	  --- Virtual Memory Subsystem ---------------------------