lkml.org 
[lkml]   [2010]   [Sep]   [15]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC][PATCH] Cross Memory Attach
    On Wed, 15 Sep 2010 10:02:35 +0200
    Ingo Molnar <mingo@elte.hu> wrote:
    >
    > What did those OpenMPI facilities use before your patch - shared
    > memory or sockets?

    This comparison is against OpenMPI using the shared memory btl.

    > I have an observation about the interface:
    >
    > A small detail: 'int flags' should probably be 'unsigned long flags'
    > - it leaves more space.

    ok.

    > Also, note that there is a further performance optimization possible
    > here: if the other task's ->mm is the same as this task's (they share
    > the MM), then the copy can be done straight in this process context,
    > without GUP. User-space might not necessarily be aware of this so it
    > might make sense to express this special case in the kernel too.

    ok.

    > More fundamentally, wouldnt it make sense to create an iovec
    > interface here? If the Gather(v) / Scatter(v) / AlltoAll(v) workloads
    > have any fragmentation on the user-space buffer side then the copy of
    > multiple areas could be done in a single syscall. (the MM lock has to
    > be touched only once, target task only be looked up only once, etc.)

    yes, I think so. Currently where I'm using the interface in OpenMPI I
    can't take advantage of this, but it could be changed in the future- and
    its likely other MPI's could take advantage of it already.

    > Plus, a small naming detail, shouldnt the naming be more IO like:
    >
    > sys_process_vm_read()
    > sys_process_vm_write()

    Yes, that looks better to me. I really wasn't sure how to name them.

    Regards,

    Chris
    --
    cyeoh@au.ibm.com


    \
     
     \ /
      Last update: 2010-09-15 15:23    [W:0.021 / U:30.900 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site