Date: Mon, 12 Oct 2015 19:39:04 -0400 From: suresh gumpula <gsuryacse7k@gmail.com> To: alc@freebsd.org Cc: "freebsd-hackers@freebsd.org" <freebsd-hackers@freebsd.org> Subject: Re: kernel pages superpage promotion/demotion Message-ID: <CAJOqHmjfG7%2BFuNZR_hNH8f-2isK1-Pv4Oma80rMhi_8yDQ9jCQ@mail.gmail.com> In-Reply-To: <CAJUyCcO2DgGE%2BYhmSiZw7nK3-3EBPsHHhH0xhfy98MfQeWTQMg@mail.gmail.com> References: <CAJOqHmitGr2oEnNheoG2MQYVcwsPNFyPHqhsTA%2BsAC40Yqw0Rg@mail.gmail.com> <CAJUyCcO2DgGE%2BYhmSiZw7nK3-3EBPsHHhH0xhfy98MfQeWTQMg@mail.gmail.com>
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Thanks a lot for quick reply Alan. The super page promotion/demotion of kernel allocations is done in 9.1 also I assume . Please confirm. Regarding write protection, I am trying to chase a corruption of uma zone allocation, so I was looking at pmap_protect(9). And thinking of using something like pmap_protect(kernel_pmap, sva , eva, VMPROT_READ); to write protect sva to eva of a zone allocation return address. So can pmap_protect(9) be used for this purpose ? Thanks Suresh On Mon, Oct 12, 2015 at 6:43 PM, Alan Cox <alan.l.cox@gmail.com> wrote: > > > 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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