Date: Mon, 12 Oct 2015 17:43:49 -0500 From: Alan Cox <alan.l.cox@gmail.com> To: suresh gumpula <gsuryacse7k@gmail.com> Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: kernel pages superpage promotion/demotion Message-ID: <CAJUyCcO2DgGE%2BYhmSiZw7nK3-3EBPsHHhH0xhfy98MfQeWTQMg@mail.gmail.com> In-Reply-To: <CAJOqHmitGr2oEnNheoG2MQYVcwsPNFyPHqhsTA%2BsAC40Yqw0Rg@mail.gmail.com> References: <CAJOqHmitGr2oEnNheoG2MQYVcwsPNFyPHqhsTA%2BsAC40Yqw0Rg@mail.gmail.com>
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On Mon, Oct 12, 2015 at 3:11 PM, suresh gumpula <gsuryacse7k@gmail.com> wrote: > Hi, > I understand that user space VM map pages dynamically > promoted/demoted to super page > if the kernel thinks that it gains the performance. > The question is , does this apply to kernel map pages too ? > > Yes, it applies to memory allocated for UMA zones, malloc(9), and contigmalloc(9). > And is it possible to write protect kernel address space VA with > pmap_protect(9). Since the protection is per 4k page, I see this > routine tries to demote to 4k page. > Or this is only for user space maps to support mprotect(2) and gdb > watchpoints. > Do we have any other API to write protect kernel addresses which come from > UMA zone allocations ? > > No. Can you please try to describe what are you trying to do at a higher level?
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