Messages in this thread | | | Date | Wed, 28 Sep 2022 17:56:56 -0300 | Subject | Re: [PATCH] x86/split_lock: Restore warn mode (and add a new one) to avoid userspace regression | From | "Guilherme G. Piccoli" <> |
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On 28/09/2022 17:24, Luck, Tony wrote: > [...] > Why not just use the workaround suggested in that bug report: > > "so manual switching from default setting to split_lock_detect=off helps as workaround here" > > If you add this extra mode, I'm going to argue that the kernel default > should be "seq" rather than "warn". So these game players will need > to add a split_lock_detect=off (or warn) option. >
Hi Tony, thanks for your response. The workaround is the way to circumvent the issue for now, but not all users want (or know how) to deal with the kernel parameters. If a distro wants to default to show a warning only, but don't break performance so hard, this would be currently impossible.
I understand that maybe the kernel default could be seq, I could re-submit - not a deal breaker, at least distros are given a way to collect split lock reports without breaking!
The main/big issues here are two: defaulting to the disruptive behavior (with no way of building a kernel not defaulting to that without patching), and not having a way to warn about split locking without breaking the performance, hence the new mode "seq".
> Has a bug report been filed against the God Of War game? Probably worth fixing, > the performance penalty for split lock is only going to get worse as numbers of > cores keeps increasing. >
Definitely worth fixing! And the plan is always to report it - meanwhile, we'd like to have all users of old/proprietary software/games to continue using the kernel the way it was before :-)
Regarding God of War specifically, I'm not sure but I can verify - the devels should be made aware, for sure.
Cheers,
Guilherme
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