lkml.org 
[lkml]   [2007]   [Nov]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC 5/7] LTTng instrumentation mm
    * Dave Hansen (haveblue@us.ibm.com) wrote:
    > On Thu, 2007-11-15 at 16:51 -0500, Mathieu Desnoyers wrote:
    > > * Dave Hansen (haveblue@us.ibm.com) wrote:
    > > > > On Tue, 2007-11-13 at 14:33 -0500, Mathieu Desnoyers wrote:
    > > > > linux-2.6-lttng/mm/page_io.c 2007-11-13 09:49:35.000000000 -0500
    > > > > @@ -114,6 +114,7 @@ int swap_writepage(struct page *page, st
    > > > > rw |= (1 << BIO_RW_SYNC);
    > > > > count_vm_event(PSWPOUT);
    > > > > set_page_writeback(page);
    > > > > + trace_mark(mm_swap_out, "address %p", page_address(page));
    > > > > unlock_page(page);
    > > > > submit_bio(rw, bio);
    > > > > out:
    > > >
    > > > I'm not sure all this page_address() stuff makes any sense on highmem
    > > > systems. How about page_to_pfn()?
    > >
    > > Knowing which page frame number has been swapped out is not always as
    > > relevant as knowing the page's virtual address (when it has one). Saving
    > > both the PFN and the page's virtual address could give us useful
    > > information when the page is not mapped.
    >
    > For most (all?) architectures, the PFN and the virtual address in the
    > kernel's linear are interchangeable with pretty trivial arithmetic. All
    > pages have a pfn, but not all have a virtual address. Thus, I suggested
    > using the pfn. What kind of virtual addresses are you talking about?
    >

    Hrm, in asm-generic/memory_model.h, we have various versions of
    __page_to_pfn. Normally they all cast the result to (unsigned long),
    except for :


    #elif defined(CONFIG_SPARSEMEM_VMEMMAP)

    /* memmap is virtually contigious. */
    #define __pfn_to_page(pfn) (vmemmap + (pfn))
    #define __page_to_pfn(page) ((page) - vmemmap)

    So I guess the result is a pointer ? Should this be expected ?

    Mathieu

    --
    Mathieu Desnoyers
    Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
    OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
    -
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2007-11-16 15:51    [W:0.028 / U:33.700 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site