Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-15 Thread Nicholas Piggin
Excerpts from Andy Lutomirski's message of July 14, 2020 10:46 pm: > > >> On Jul 13, 2020, at 11:31 PM, Nicholas Piggin wrote: >> >> Excerpts from Nicholas Piggin's message of July 14, 2020 3:04 pm: >>> Excerpts from Andy Lutomirski's message of July 14, 2020 4:18 am: > On Jul 13,

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-15 Thread Nicholas Piggin
Excerpts from Andy Lutomirski's message of July 14, 2020 10:46 pm: > > >> On Jul 13, 2020, at 11:31 PM, Nicholas Piggin wrote: >> >> Excerpts from Nicholas Piggin's message of July 14, 2020 3:04 pm: >>> Excerpts from Andy Lutomirski's message of July 14, 2020 4:18 am: > On Jul 13,

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-14 Thread Peter Zijlstra
On Tue, Jul 14, 2020 at 05:46:05AM -0700, Andy Lutomirski wrote: > x86 has this exact problem. At least no more than 64*8 CPUs share the cache > line :) I've seen patches for a 'sparse' bitmap to solve related problems. It's basically the same code, except it multiplies everything (size,

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-14 Thread Andy Lutomirski
> On Jul 13, 2020, at 11:31 PM, Nicholas Piggin wrote: > > Excerpts from Nicholas Piggin's message of July 14, 2020 3:04 pm: >> Excerpts from Andy Lutomirski's message of July 14, 2020 4:18 am: >>> On Jul 13, 2020, at 9:48 AM, Nicholas Piggin wrote: Excerpts from Andy

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-14 Thread Nicholas Piggin
Excerpts from Nicholas Piggin's message of July 14, 2020 3:04 pm: > Excerpts from Andy Lutomirski's message of July 14, 2020 4:18 am: >> >>> On Jul 13, 2020, at 9:48 AM, Nicholas Piggin wrote: >>> >>> Excerpts from Andy Lutomirski's message of July 14, 2020 1:59 am: > On Thu, Jul 9, 2020

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-13 Thread Nicholas Piggin
Excerpts from Andy Lutomirski's message of July 14, 2020 4:18 am: > >> On Jul 13, 2020, at 9:48 AM, Nicholas Piggin wrote: >> >> Excerpts from Andy Lutomirski's message of July 14, 2020 1:59 am: On Thu, Jul 9, 2020 at 6:57 PM Nicholas Piggin wrote: On big systems, the mm

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-13 Thread Andy Lutomirski
> On Jul 13, 2020, at 9:48 AM, Nicholas Piggin wrote: > > Excerpts from Andy Lutomirski's message of July 14, 2020 1:59 am: >>> On Thu, Jul 9, 2020 at 6:57 PM Nicholas Piggin wrote: >>> >>> On big systems, the mm refcount can become highly contented when doing >>> a lot of context switching

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-13 Thread Nicholas Piggin
Excerpts from Andy Lutomirski's message of July 14, 2020 1:59 am: > On Thu, Jul 9, 2020 at 6:57 PM Nicholas Piggin wrote: >> >> On big systems, the mm refcount can become highly contented when doing >> a lot of context switching with threaded applications (particularly >> switching between the

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-13 Thread Andy Lutomirski
On Thu, Jul 9, 2020 at 6:57 PM Nicholas Piggin wrote: > > On big systems, the mm refcount can become highly contented when doing > a lot of context switching with threaded applications (particularly > switching between the idle thread and an application thread). > > Abandoning lazy tlb slows

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-12 Thread Nicholas Piggin
Excerpts from Peter Zijlstra's message of July 10, 2020 7:35 pm: > On Fri, Jul 10, 2020 at 11:56:46AM +1000, Nicholas Piggin wrote: >> On big systems, the mm refcount can become highly contented when doing >> a lot of context switching with threaded applications (particularly >> switching between

Re: [RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-10 Thread Peter Zijlstra
On Fri, Jul 10, 2020 at 11:56:46AM +1000, Nicholas Piggin wrote: > On big systems, the mm refcount can become highly contented when doing > a lot of context switching with threaded applications (particularly > switching between the idle thread and an application thread). > > Abandoning lazy tlb

[RFC PATCH 7/7] lazy tlb: shoot lazies, a non-refcounting lazy tlb option

2020-07-09 Thread Nicholas Piggin
On big systems, the mm refcount can become highly contented when doing a lot of context switching with threaded applications (particularly switching between the idle thread and an application thread). Abandoning lazy tlb slows switching down quite a bit in the important user->idle->user cases, so