lkml.org 
[lkml]   [2014]   [Jul]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    SubjectRE: scsi-mq V2
    Date


    > -----Original Message-----
    > From: Christoph Hellwig [mailto:hch@infradead.org]
    > Sent: Thursday, 10 July, 2014 11:15 AM
    > To: Elliott, Robert (Server Storage)
    > Cc: Jens Axboe; dgilbert@interlog.com; James Bottomley; Bart Van Assche;
    > Benjamin LaHaise; linux-scsi@vger.kernel.org; linux-kernel@vger.kernel.org
    > Subject: Re: scsi-mq V2
    >
    > On Thu, Jul 10, 2014 at 09:04:22AM -0700, Christoph Hellwig wrote:
    > > It's starting to look weird. I'll prepare another two bisect branches
    > > around some MM changes, which seems the only other possible candidate.
    >
    > I've pushed out scsi-mq.3-bisect-3

    Good.

    > and scsi-mq.3-bisect-4 for you.

    Bad.

    Note: I had to apply the vdso2c.h patch to build this -rc3 based kernel:
    diff --git a/arch/x86/vdso/vdso2c.h b/arch/x86/vdso/vdso2c.h
    index df95a2f..11b65d4 100644
    --- a/arch/x86/vdso/vdso2c.h
    +++ b/arch/x86/vdso/vdso2c.h
    @@ -93,6 +93,9 @@ static void BITSFUNC(copy_section)(struct BITSFUNC(fake_sections) *out,
    uint64_t flags = GET_LE(&in->sh_flags);

    bool copy = flags & SHF_ALLOC &&
    + (GET_LE(&in->sh_size) ||
    + (GET_LE(&in->sh_type) != SHT_RELA &&
    + GET_LE(&in->sh_type) != SHT_REL)) &&
    strcmp(name, ".altinstructions") &&
    strcmp(name, ".altinstr_replacement");

    Results: fio started OK, getting 900K IOPS, but ^C led to 0 IOPS and
    an fio hang, with one CPU (CPU 0) stuck in io_submit loops.

    perf top shows lookup_ioctx function alongside io_submit and
    do_io_submit this time:
    14.96% [kernel] [k] lookup_ioctx
    14.71% libaio.so.1.0.1 [.] io_submit
    13.78% [kernel] [k] system_call
    10.79% [kernel] [k] system_call_after_swapgs
    10.17% [kernel] [k] do_io_submit
    8.91% [kernel] [k] copy_user_generic_string
    4.24% [kernel] [k] io_submit_one
    3.93% [kernel] [k] blk_flush_plug_list
    3.32% fio [.] fio_libaio_commit
    2.84% [kernel] [k] sysret_check
    2.06% [kernel] [k] blk_finish_plug
    1.89% [kernel] [k] SyS_io_submit
    1.48% [kernel] [k] blk_start_plug
    1.04% fio [.] io_submit@plt
    0.84% [kernel] [k] __get_user_4
    0.74% [kernel] [k] system_call_fastpath
    0.60% [kernel] [k] _copy_from_user
    0.51% diff [.] 0x0000000000007abb
    ftrace on CPU 0 shows similar repetition to before:
    fio-4107 [000] .... 389.992300: lookup_ioctx <-do_io_submit
    fio-4107 [000] .... 389.992300: blk_start_plug <-do_io_submit
    fio-4107 [000] .... 389.992300: io_submit_one <-do_io_submit
    fio-4107 [000] .... 389.992300: blk_finish_plug <-do_io_submit
    fio-4107 [000] .... 389.992300: blk_flush_plug_list <-blk_finish_plug
    fio-4107 [000] .... 389.992301: SyS_io_submit <-system_call_fastpath
    fio-4107 [000] .... 389.992301: do_io_submit <-SyS_io_submit
    fio-4107 [000] .... 389.992301: lookup_ioctx <-do_io_submit
    fio-4107 [000] .... 389.992301: blk_start_plug <-do_io_submit
    fio-4107 [000] .... 389.992301: io_submit_one <-do_io_submit
    fio-4107 [000] .... 389.992301: blk_finish_plug <-do_io_submit
    fio-4107 [000] .... 389.992301: blk_flush_plug_list <-blk_finish_plug
    fio-4107 [000] .... 389.992301: SyS_io_submit <-system_call_fastpath
    fio-4107 [000] .... 389.992302: do_io_submit <-SyS_io_submit
    fio-4107 [000] .... 389.992302: lookup_ioctx <-do_io_submit
    fio-4107 [000] .... 389.992302: blk_start_plug <-do_io_submit
    fio-4107 [000] .... 389.992302: io_submit_one <-do_io_submit
    fio-4107 [000] .... 389.992302: blk_finish_plug <-do_io_submit
    fio-4107 [000] .... 389.992302: blk_flush_plug_list <-blk_finish_plug




    \
     
     \ /
      Last update: 2014-07-11 05:41    [W:2.063 / U:0.104 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site