Hi John, On Feb 10, 2011, at 5:33 PM, John Mainzer wrote:
>> From [email protected] Thu Feb 10 16:48:04 2011 >> From: Rhys Ulerich <[email protected]> >> Date: Thu, 10 Feb 2011 16:48:22 -0600 >> To: HDF Users Discussion List <[email protected]> >> Subject: [Hdf-forum] Question re: Howison et al Lustre mdc_config tuning >> recommendations >> >> Good day, >> >> I decided to try some metadata caching parameters related to the >> discussion on pages 3-4 of Howison et al >> (http://www.hdfgroup.org/pubs/papers/howison_hdf5_lustre_iasds2010.pdf). >> The paper gives sample code as follows in Figure 5: >> >> H5AC_cache_config_t mdc_config; >> hid_t file_id; >> file_id = H5Fopen("file.h5", H5ACC_RDWR, H5P_DEFAULT); >> mdc_config.version = H5AC__CURR_CACHE_CONFIG_VERSION; >> H5Pget_mdc_config(file_id, &mdc_config) >> mdc_config.evictions_enabled = 0 /* FALSE */; >> mdc_config.incr_mode = H5C_incr__off; >> mdc_config.decr_mode = H5C_decr__off; >> H5Pset_mdc_config(file_id, &mdc_config); >> >> Attempting to directly implement this fails. Modifying the above so >> the H5Pget_mdc_config/H5Pset_mdc_config operates on a file access >> property list succeeds. However, I saw runtime errors like >> >> HDF5-DIAG: Error detected in HDF5 (1.8.5-patch1) MPI-process 2: >> #000: H5Pfapl.c line 1354 in H5Pset_mdc_config(): invalid metadata >> cache configuration >> major: Invalid arguments to routine >> minor: Bad value >> #001: H5AC.c line 2665 in H5AC_validate_config(): Can't disable >> evictions while auto-resize is enabled. >> major: Invalid arguments to routine >> minor: Bad value >> >> which I've remedied by glancing at H5AC.c:2665 and then adding the statement >> >> mdc_config.flash_incr_mode = H5C_flash_incr__off; >> >> to the code block above. Is this modification in the spirit of what >> Howison et al. suggests? Or is using H5C_flash_incr__off asking for >> trouble in ways that the paper does not discuss? >> >> Thanks for your time, >> Rhys >> >> _______________________________________________ >> Hdf-forum is for HDF software users discussion. >> [email protected] >> http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org > > Hi Rhys, > > You did exactly as you should have. > > The metadata cache configuration in the paper worked due to an error > on my part when I implemented the flash cache size increment code. I have > since noticed and correct the error -- hence the failure you encountered > when you tried to duplicate the code from the paper. Is this fix included in the 1.8.6 release? Thanks, Quincey > To give you some background: > > In its default configuration, the metadata cache in HDF5 will attempt to > automatically adapt to the current metadata working set size in real time. > While there is no fundamental reason why this feature can't be active when > evictions are disabled, I can't think of any circumstances in which it would > be useful. Further, writing the test code required to verify proper behavior > under these circumstances would require significant effort. > > Hence the decision to require that adaptive metadata cache resizing be > disabled when evictions are disabled. Needless to say, this decision will > be re-visited if anyone comes up with a plausible reason to do so. > > Best regards, > > John Mainzer > > _______________________________________________ > Hdf-forum is for HDF software users discussion. > [email protected] > http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org _______________________________________________ Hdf-forum is for HDF software users discussion. [email protected] http://mail.hdfgroup.org/mailman/listinfo/hdf-forum_hdfgroup.org
