Dave and Rob: Yes. The modified open() via the usrint library allows a program to specify things like strip size and number of datafiles on an open that has the O_CREAT flag set. fcntl() could not be used in this situation, because once a file is created via OrangeFS these properties cannot be changed.
Dave: Thanks for the glibc info. Still trying to determine in which version of glibc this problem occurs. Becky On Tue, Jun 16, 2015 at 9:59 AM, Rob Latham <[email protected]> wrote: > > > On 06/16/2015 08:52 AM, Dave Love wrote: > >> Rob Latham <[email protected]> writes: >> >> I wasn't involved in this feature, but it looks like OrangeFS is >>> taking advantage of open() being declared with variable length >>> arguments to pass in a fourth "hint" parameter. >>> >> >> I'm still puzzled on what system that does anything. >> > > In the old days you had two ways to access PVFS: > > - make a round trip through the kernel module, bouncing through quite a > few userspace-kernelspace copies. > > - contact PVFS servers directly through the "system interface". The one > real client for the system interface is ROMIO's PVFS driver, but some of > the early utilities would use it too (maybe still do?) > > OrangeFS provides a third way: link in with the orangfs library and now > the posix open/close/read/write system calls become OrangeFS calls. no code > changes needed. You might not get a lot of parallelism out of it, but it > makes many-task non-MPI workloads (like Hadoop) easier to support. > > So, that fourth argument was a (sneaky!) attempt to set some PVFS > parameters without changing the posix-like API. The less-sneaky but gross > way to do this for most file systems is via fcntl() operations, but fcntl > is an awful interface. > > ==rob > > -- > Rob Latham > Mathematics and Computer Science Division > Argonne National Lab, IL USA > _______________________________________________ > Pvfs2-users mailing list > [email protected] > http://www.beowulf-underground.org/mailman/listinfo/pvfs2-users >
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