linux-ext4 - [PATCH 10/11] fuse2fs: constrain worker thread count

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Message-ID: <175797570193.246189.18292292585216876168.stgit@frogsfrogsfrogs>
Date: Mon, 15 Sep 2025 15:43:27 -0700
From: "Darrick J. Wong" <djwong@...nel.org>
To: tytso@....edu
Cc: linux-ext4@...r.kernel.org
Subject: [PATCH 10/11] fuse2fs: constrain worker thread count

From: Darrick J. Wong <djwong@...nel.org>

fuse2fs isn't all that scalable -- there's a big kernel lock around all
the libext2fs code.  Constrain the fuse worker thread count to reduce
unnecessary lock contention.

Signed-off-by: "Darrick J. Wong" <djwong@...nel.org>
---
 misc/fuse2fs.c |    8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/misc/fuse2fs.c b/misc/fuse2fs.c
index 1f2700b5f95270..e54a2d7f9ae523 100644
--- a/misc/fuse2fs.c
+++ b/misc/fuse2fs.c
@@ -5102,6 +5102,14 @@ int main(int argc, char *argv[])
  "-oallow_other,default_permissions,suid,dev");
 	}

+	/*
+	 * Since there's a Big Kernel Lock around all the libext2fs code, we
+	 * only need to start four threads -- one to decode a request, another
+	 * to do the filesystem work, a third to transmit the reply, and a
+	 * fourth to handle fuse notifications.
+	 */
+	fuse_opt_insert_arg(&args, 1, "-omax_threads=4");
+
 	if (fctx.debug) {
 		int	i;