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| author | Demi Marie Obenour <demi@invisiblethingslab.com> | 2023-07-26 12:52:41 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-08-03 10:24:14 +0200 |
| commit | cd1a8952ff529adc210e62306849fd6f256608c0 (patch) | |
| tree | 99d0207edbf826cca0f7a14ab185524db77c4d21 /Documentation | |
| parent | af7aa4fe94b3dc0652f7fb5369f78623e98b0310 (diff) | |
| download | linux-cd1a8952ff529adc210e62306849fd6f256608c0.tar.gz | |
xen: speed up grant-table reclaim
commit c04e9894846c663f3278a414f34416e6e45bbe68 upstream. When a grant entry is still in use by the remote domain, Linux must put it on a deferred list. Normally, this list is very short, because the PV network and block protocols expect the backend to unmap the grant first. However, Qubes OS's GUI protocol is subject to the constraints of the X Window System, and as such winds up with the frontend unmapping the window first. As a result, the list can grow very large, resulting in a massive memory leak and eventual VM freeze. To partially solve this problem, make the number of entries that the VM will attempt to free at each iteration tunable. The default is still 10, but it can be overridden via a module parameter. This is Cc: stable because (when combined with appropriate userspace changes) it fixes a severe performance and stability problem for Qubes OS users. Cc: stable@vger.kernel.org Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com> Reviewed-by: Juergen Gross <jgross@suse.com> Link: https://lore.kernel.org/r/20230726165354.1252-1-demi@invisiblethingslab.com Signed-off-by: Juergen Gross <jgross@suse.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/ABI/testing/sysfs-module | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Documentation/ABI/testing/sysfs-module b/Documentation/ABI/testing/sysfs-module index 08886367d047..62addab47d0c 100644 --- a/Documentation/ABI/testing/sysfs-module +++ b/Documentation/ABI/testing/sysfs-module @@ -60,3 +60,14 @@ Description: Module taint flags: C staging driver module E unsigned module == ===================== + +What: /sys/module/grant_table/parameters/free_per_iteration +Date: July 2023 +KernelVersion: 6.5 but backported to all supported stable branches +Contact: Xen developer discussion <xen-devel@lists.xenproject.org> +Description: Read and write number of grant entries to attempt to free per iteration. + + Note: Future versions of Xen and Linux may provide a better + interface for controlling the rate of deferred grant reclaim + or may not need it at all. +Users: Qubes OS (https://www.qubes-os.org) |