From 29bd22171adcbf79b118885df7f46dedf5016f78 Mon Sep 17 00:00:00 2001 From: carns Date: Thu, 8 Nov 2012 21:46:37 +0000 Subject: [PATCH] update runtime docs to reflect --enable-stat-at-open option git-svn-id: https://svn.mcs.anl.gov/repos/darshan/trunk@617 3b7491f3-a168-0410-bf4b-c445ed680a29 --- darshan-runtime/doc/darshan-runtime.txt | 21 +++++++++++++++------ 1 file changed, 15 insertions(+), 6 deletions(-) diff --git a/darshan-runtime/doc/darshan-runtime.txt b/darshan-runtime/doc/darshan-runtime.txt index 1537811..7c40c51 100644 --- a/darshan-runtime/doc/darshan-runtime.txt +++ b/darshan-runtime/doc/darshan-runtime.txt @@ -40,6 +40,20 @@ make make install ---- +.Detecting file size and alignment +[NOTE] +==== +You can also add --enable-stat-at-open option to cause the Darshan library +to issue an additional stat() system call on each file the first time that +it is opened on each process. This allows Darshan to detect the file +alignment (and subsequent unaligned accesses). It also allows Darshan to +detect the size of files at open time before any I/O is performed. +Unfortunately, this option can cause significant overhead at scale on file +systems such as PVFS or Lustre that must contact every server for a given +file in order to satisfy a stat request. We therefore disable this +feature by default. +==== + .Explanation of configure arguments: * `--with-mem-align` (mandatory): This value is system-dependent and will be used by Darshan to determine if the buffer for a read or write operation is @@ -236,7 +250,7 @@ module swap PrgEnv-pgi PrgEnv-gnu ./configure --with-mem-align=8 \ --with-log-path=/shared-file-system/darshan-logs \ --prefix=/soft/darshan-2.2.3 \ - --with-jobid-env=PBS_JOBID --disable-cuserid --enable-st-dev-workaround CC=cc + --with-jobid-env=PBS_JOBID --disable-cuserid CC=cc make install module swap PrgEnv-gnu PrgEnv-pgi ---- @@ -254,11 +268,6 @@ but on some Cray environments (notably the Beagle XE6 system as of March 2012) the cuserid() call triggers a segmentation fault. With this option set, Darshan will typically use the LOGNAME environment variable to determine a userid. - -The --enable-st-dev-workaround argument is used to tell Darshan to -determine the device type of each file by checking the parent directory -rather than the file itself. This is a workaround for a file stat -inconsistency observed on some systems. ==== As in any Darshan installation, the darshan-mk-log-dirs.pl script can then be -- 2.26.2