lkml.org 
[lkml]   [2021]   [Jul]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH AUTOSEL 5.12 42/43] virtio: fix up virtio_disable_cb
On Sun, Jul 11, 2021 at 12:23:59AM -0400, Michael S. Tsirkin wrote:
>On Sat, Jul 10, 2021 at 07:49:14PM -0400, Sasha Levin wrote:
>> From: "Michael S. Tsirkin" <mst@redhat.com>
>>
>> [ Upstream commit 8d622d21d24803408b256d96463eac4574dcf067 ]
>>
>> virtio_disable_cb is currently a nop for split ring with event index.
>> This is because it used to be always called from a callback when we know
>> device won't trigger more events until we update the index. However,
>> now that we run with interrupts enabled a lot we also poll without a
>> callback so that is different: disabling callbacks will help reduce the
>> number of spurious interrupts.
>> Further, if using event index with a packed ring, and if being called
>> from a callback, we actually do disable interrupts which is unnecessary.
>>
>> Fix both issues by tracking whenever we get a callback. If that is
>> the case disabling interrupts with event index can be a nop.
>> If not the case disable interrupts. Note: with a split ring
>> there's no explicit "no interrupts" value. For now we write
>> a fixed value so our chance of triggering an interupt
>> is 1/ring size. It's probably better to write something
>> related to the last used index there to reduce the chance
>> even further. For now I'm keeping it simple.
>>
>> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
>> Signed-off-by: Sasha Levin <sashal@kernel.org>
>
>I am not sure we want this in stable yet. It should in theory
>fix the reported interrupt storms but the reporter is on vacation.

Sure, I'll drop it for now. Let me know when you want it re-added.
Thanks!

--
Thanks,
Sasha

\
 
 \ /
  Last update: 2021-07-18 03:42    [W:0.047 / U:0.904 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site