lkml.org 
[lkml]   [2010]   [May]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    From
    Date
    SubjectRE: acpi_idle: Very idle Core i7 machine never enters C3


    > -----Original Message-----
    > From: Len Brown [mailto:lenb@kernel.org]
    > Sent: Tuesday, May 25, 2010 1:43 PM
    > To: Philip Langdale
    > Cc: Matthew Garrett; Jeff Garrett; Andi Kleen; Linux Kernel Mailing
    > List; linux-acpi@vger.kernel.org; Yu, Luming; venki@google.com
    > Subject: Re: acpi_idle: Very idle Core i7 machine never enters C3
    >
    > > >> I am hopeful that the "right thing to do" is to not look at bm-
    > status
    > > >> and that perhaps there is a bug where we are looking at it
    > > >> "by mistake".
    > > >
    > > > https://patchwork.kernel.org/patch/58962/ - it seems to be a win.
    > >
    > > Indeed. This patch does solve the C6 problem. I'm not in a position
    > to
    > > speak about whether there's any undesirable I/O latency, but it
    > > passes the basic sanity check.
    > >
    > > I have filed https://bugzilla.kernel.org/show_bug.cgi?id=15886 with
    > > my acpi dump - assuming that's still useful.
    >
    > Luming's patch above basically deletes acpi_idle_bm_check() --
    > the BM_STS check -- from the C3 path on all Intel SMP boxes.
    > This is effectively the same as my test patch
    > https://patchwork.kernel.org/patch/77370/
    > that made acpi_idle_bm_check() do nothing.
    >
    > I'm told by the hardware guys that BM_STS is _not_ always
    > a NOP, and so we're not supposed to simply ignore it on C3 --
    > though it should be extremely rare that we see it set.

    On some platforms like NHM-EX, I was told that it's a NOP,
    But I might be given wrong information at that time when I wrote that patch.

    IIRC, acpi spec just say it's optional..

    Thanks,
    Luming


    \
     
     \ /
      Last update: 2010-05-25 08:07    [W:0.035 / U:31.532 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site