[ROOT] Concurrent access to multiple TFiles and gDirectory

From: Brandon Kohn (blk@maia-institute.org)
Date: Wed Jan 28 2004 - 11:16:42 MET

Hello Rooters,

I was wondering if anyone here had any experience with using TFiles in a
multi-threaded application or if this is even possible given the current use
of the global gDirectory. I'm interested in implementing a single
application that will contain one thread writing to a TFile, whilst allowing
another to serve data (from a different TFile) for browsing by users. My
understanding of the current IO system's implementation would seem to
require that all file accesses would have to be atomic at the level of the
calls to root.

The first problem that I see with this, is that such locking would likely
remove much of the benefit of multithreading because the blocking mechanism
wouldn't release the locks during the actual system level IO (which is
exactly where you're likely to see some performance improvements.)

Does anyone have some information about using ROOT in this way?

Thanks for any help...

Brandon Kohn                        Tel.: +377 97 97 41 51
Software Engineer/Sys Admin
The Maia Institute                   Fax.: +377 97 97 41 59
Le Patio Palace

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