Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1718626

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

Show all headers | View raw

On Wed, Aug 23, 2017 at 11:26:46AM -0700, Linus Torvalds wrote:
> On Wed, Aug 23, 2017 at 6:45 AM, Vitaly Kuznetsov <vkuznets@redhat.com> 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 unconditional if it doesn't really
> show any performance difference. One less config complexity to worry
> about (and in this case I'm not so much worried about Kconfig itself,
> as just "oh, you have totally different paths in the core VM depending
> on PARAVIRT".

In this case we need performance numbers for !PARAVIRT kernel.

> That said, the thing to test for these kinds of things is often
> heavily scripted loads that just run thousands and thousands of really
> small processes, and build up and tear down page tables all the time
> because of fork/exit.
> 
> The load I've used occasionally is just "make test" in the git source
> tree. Tons and tons of trivial fork/exec/exit things for all those
> small tests and shell scripts.

Numbers for tight loop of "mmap(MAP_POPULATE); munmap()" might be
interesting too for worst case scenario.

-- 
 Kirill A. Shutemov

Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread

Thread

[PATCH] x86: enable RCU based table free when PARAVIRT Vitaly Kuznetsov <vkuznets@redhat.com> - 2017-08-23 15:50 +0200
  Re: [PATCH] x86: enable RCU based table free when PARAVIRT Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-23 20:30 +0200
    Re: [PATCH] x86: enable RCU based table free when PARAVIRT "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-23 22:10 +0200
      Re: [PATCH] x86: enable RCU based table free when PARAVIRT Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-23 22:30 +0200
        Re: [PATCH] x86: enable RCU based table free when PARAVIRT "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2017-08-24 00:40 +0200
          Re: [PATCH] x86: enable RCU based table free when PARAVIRT Linus Torvalds <torvalds@linux-foundation.org> - 2017-08-24 01:10 +0200
            Re: [PATCH] x86: enable RCU based table free when PARAVIRT "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-24 10:50 +0200
            Re: [PATCH] x86: enable RCU based table free when PARAVIRT Vitaly Kuznetsov <vkuznets@redhat.com> - 2017-08-24 10:50 +0200

csiph-web