Hello John, please note that the Lustre client does not write data to a disk device, rather it sends and receives data through network, particularly, through a socket in case of ksocklnd. Even if the call may not be considered slow with respect to indefiniteness, it still is slow as compared to the "fast I/O" (local disk I/O). I can recall several requests of adding even more interruption points made by people who were looking for the support of premature read/write termination (and, I believe, l_wait_event usage in 1.8 is such that since a network request has been sent, the read/write system call cannot be interrupted until the corresponding lustre timeout has happened or a reply has been received)
Best wishes, Andrew. >On 07/08/2010 08:53 AM, Kevin Van Maren wrote: >It also says "The issue of which files or file types are interruptible >is considered an implementation design issue. This is often affected >primarily by hardware and reliability issues." > >For Linux, the signal(7) manpage indicates that read(2), readv(2), >write(2), writev(2), and ioctl(2) calls on "slow" devices should return >-EINTR when interrupted by a signal, and goes on to say that "slow" >devices are ones "where the I/O call may block for an indefinite time, >for example, a terminal, pipe, or socket. (A disk is not a slow device >according to this definition.)" > >Nowhere does it say something really helpfully clear like "Writing to a >regular file shall suspend the calling process until such time as..." >But, I interpret this to mean that operations on regular files are not >interruptible, and should not return -EINTR. Moreover, I understand >that this is the consensus among those unlucky enough to care. > >On the other hand, there are some explicitly specified situations which >will result in short writes to a regular file, like file size limits. -- John L. Hammond, Ph.D. ICES, The University of Texas at Austin jhammond at ices.utexas.edu <http://lists.lustre.org/mailman/listinfo/lustre-discuss> (512) 471-9304
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