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-rw-r--r--gnu/system/vm.scm18
1 files changed, 14 insertions, 4 deletions
diff --git a/gnu/system/vm.scm b/gnu/system/vm.scm
index 3d0935b3af..1efae7ff06 100644
--- a/gnu/system/vm.scm
+++ b/gnu/system/vm.scm
@@ -88,6 +88,13 @@
;;;
;;; Code:
+;; By default, the msize value is 8 KiB, which according to QEMU is
+;; insufficient and would degrade performance. The msize value should roughly
+;; match the bandwidth of the system's IO (see:
+;; https://wiki.qemu.org/Documentation/9psetup#msize). Use 100 MiB as a
+;; conservative default.
+(define %default-msize-value (* 100 (expt 2 20))) ;100 MiB
+
(define %linux-vm-file-systems
;; File systems mounted for 'derivation-in-linux-vm'. These are shared with
;; the host over 9p.
@@ -103,21 +110,23 @@
(type "9p")
(needed-for-boot? #t)
(flags '(read-only))
- (options "trans=virtio,cache=loose")
+ (options (format #f "trans=virtio,cache=loose,msize=~a"
+ %default-msize-value))
(check? #f))
(file-system
(mount-point "/xchg")
(device "xchg")
(type "9p")
(needed-for-boot? #t)
- (options "trans=virtio")
+ (options (format #f "trans=virtio,msize=~a" %default-msize-value))
(check? #f))
(file-system
(mount-point "/tmp")
(device "tmp")
(type "9p")
(needed-for-boot? #t)
- (options "trans=virtio,cache=loose")
+ (options (format #f "trans=virtio,cache=loose,msize=~a"
+ %default-msize-value))
(check? #f))))
(define not-config?
@@ -581,7 +590,8 @@ the operating system."
(type "9p")
(flags (if writable? '() '(read-only)))
(options (string-append "trans=virtio"
- (if writable? "" ",cache=loose")))
+ (if writable? "" ",cache=loose")
+ ",msize=" (number->string %default-msize-value)))
(check? #f)
(create-mount-point? #t)))))