lkml.org 
[lkml]   [2002]   [Dec]   [17]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: Intel P6 vs P7 system call performance
    Benjamin LaHaise wrote:
    > On Tue, Dec 17, 2002 at 10:57:29AM -0800, Ulrich Drepper wrote:
    >
    >>But this is exactly what I expect to happen. If you want to implement
    >>gettimeofday() at user-level you need to modify the page. Some of the
    >>information the kernel has to keep for the thread group can be stored in
    >>this place and eventually be used by some uerlevel code executed by
    >>jumping to 0xfffff000 or whatever the address is.
    >
    >
    > You don't actually need to modify the page, rather the data for the user
    > level gettimeofday needs to be in a shared page and some register (like
    > %tr) must expose the current cpu number to index into the data. Either
    > way, it's an internal implementation detail for the kernel to take care
    > of, with multiple potential solutions.
    >

    That's not the problem... the problem is that the userland code can get
    preempted at any time and rescheduled on another CPU.

    -hpa


    -
    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: 2005-03-22 13:31    [W:0.021 / U:157.716 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site