search for: 4d92f50249eb

...on s390 yielding to the hypervisor. As it turns out this made stop_machine run really slow on virtualized overcommited systems. For example the kprobes test during bootup took several seconds instead of just running unnoticed with large guests. Therefore, the yielding was reintroduced with commit 4d92f50249eb ("s390: reintroduce diag 44 calls for cpu_relax()"), but in fact the stop machine code seems to be the only place where this yielding was really necessary. This place is probably the most important one as it makes all but one guest CPUs wait for one guest CPU. As we now have cpu_relax_yi...

...quot;s390: remove diag 44 calls from cpu_relax()") As it turns out this make stop_machine run really slow on virtualized systems. For example the kprobes test during bootup took several seconds instead of just running unnoticed with large guests. Therefore, we reintroduced that with commit 4d92f50249eb ("s390: reintroduce diag 44 calls for cpu_relax()"), but the only place where we noticed the missing yield was in the stop_machine code. I would assume that we might find some other places where this makes sense in the future, but I expect that we have much less places for yield than we...

On Fri, Oct 21, 2016 at 01:58:55PM +0200, Christian Borntraeger wrote: > stop_machine can take a very long time if the hypervisor does > overcommitment for guest CPUs. When waiting for "the one", lets > give up our CPU by using the new cpu_relax_yield. This seems something that would apply to most other virt stuff. Lets Cc a few more lists for that. > Signed-off-by:

On Fri, Oct 21, 2016 at 01:58:55PM +0200, Christian Borntraeger wrote: > stop_machine can take a very long time if the hypervisor does > overcommitment for guest CPUs. When waiting for "the one", lets > give up our CPU by using the new cpu_relax_yield. This seems something that would apply to most other virt stuff. Lets Cc a few more lists for that. > Signed-off-by:

Peter, here is v2 with some improved patch descriptions and some fixes. The previous version has survived one day of linux-next and I only changed small parts. So unless there is some other issue, feel free to pull (or to apply the patches) to tip/locking. The following changes since commit 07d9a380680d1c0eb51ef87ff2eab5c994949e69: Linux 4.9-rc2 (2016-10-23 17:10:14 -0700) are available in

Peter, here is v2 with some improved patch descriptions and some fixes. The previous version has survived one day of linux-next and I only changed small parts. So unless there is some other issue, feel free to pull (or to apply the patches) to tip/locking. The following changes since commit 07d9a380680d1c0eb51ef87ff2eab5c994949e69: Linux 4.9-rc2 (2016-10-23 17:10:14 -0700) are available in