Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-24 Thread Kirill A. Shutemov
On Wed, Aug 23, 2017 at 04:03:53PM -0700, Linus Torvalds wrote: > On Wed, Aug 23, 2017 at 3:36 PM, Kirill A. Shutemov > wrote: > > > > Below is test cases that allocates a lot of page tables and measuare > > fork/exit time. (I'm not entirely sure it's the best way

Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-24 Thread Vitaly Kuznetsov
Linus Torvalds writes: > On Wed, Aug 23, 2017 at 3:36 PM, Kirill A. Shutemov > wrote: >> >> Below is test cases that allocates a lot of page tables and measuare >> fork/exit time. (I'm not entirely sure it's the best way to stress

Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-23 Thread Kirill A. Shutemov
On Wed, Aug 23, 2017 at 08:27:18PM +, Linus Torvalds wrote: > On Wed, Aug 23, 2017 at 12:59 PM, Kirill A. Shutemov > wrote: > > > > In this case we need performance numbers for !PARAVIRT kernel. > > Yes. > > > Numbers for tight loop of "mmap(MAP_POPULATE); munmap()"

Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-23 Thread Linus Torvalds
On Wed, Aug 23, 2017 at 3:36 PM, Kirill A. Shutemov wrote: > > Below is test cases that allocates a lot of page tables and measuare > fork/exit time. (I'm not entirely sure it's the best way to stress the > codepath.) Looks ok to me. Doing a profile (without the

Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-23 Thread Linus Torvalds
On Wed, Aug 23, 2017 at 12:59 PM, Kirill A. Shutemov wrote: > > In this case we need performance numbers for !PARAVIRT kernel. Yes. > Numbers for tight loop of "mmap(MAP_POPULATE); munmap()" might be > interesting too for worst case scenario. Actually, I don't think you

Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-23 Thread Kirill A. Shutemov
On Wed, Aug 23, 2017 at 11:26:46AM -0700, Linus Torvalds wrote: > On Wed, Aug 23, 2017 at 6:45 AM, Vitaly Kuznetsov wrote: > > > > Solve the issue by enabling RCU-based table free mechanism when PARAVIRT > > is selected in config. Testing with kernbench doesn't show any

Re: [Xen-devel] [PATCH] x86: enable RCU based table free when PARAVIRT

2017-08-23 Thread Linus Torvalds
On Wed, Aug 23, 2017 at 6:45 AM, Vitaly Kuznetsov wrote: > > Solve the issue by enabling RCU-based table free mechanism when PARAVIRT > is selected in config. Testing with kernbench doesn't show any notable > performance impact: I wonder if we should just make it