On Wednesday 02 March 2011 05:53:52 howard0su wrote: > On Wed, Mar 2, 2011 at 5:17 AM, Frank Mehnert <[email protected]> wrote: > > On Tuesday 22 February 2011 11:24:30 Howard Su wrote: > >> I am not sure how big diff this change will bring in. But I think this > >> is worth trying. I enable this unconditional because i believe the > >> most write for disk file doesn't need cache in host (guest already > >> handle it.) > >> > >> Index: VD.cpp > >> =================================================================== > >> --- VD.cpp (revision 35998) > >> +++ VD.cpp (working copy) > >> @@ -2333,7 +2333,7 @@ > >> pStorage->pfnCompleted = pfnCompleted; > >> > >> /* Open the file. */ > >> - int rc = RTFileOpen(&pStorage->File, pszLocation, fOpen); > >> + int rc = RTFileOpen(&pStorage->File, pszLocation, fOpen | > >> RTFILE_O_NO_CACHE); > >> if (RT_SUCCESS(rc)) > >> { > >> *ppStorage = pStorage; > > > > This change does not make much sense. Better disable the host I/O > > cache in the VM settings which is the correct strategy. > > That setting is only used to control disable host i/o for direct > attach raw device. It doesn't apply to the disk files you opened. this > is what I read from code. Correct me if i am wrong.
Yes, you are wrong :) If you disable the host cache for a storage controller, all attached mediums will use asynchronous I/O and will access the host medium with O_DIRECT. There are a few exceptions (AFAIR for example NFS) but it should be visible in the VBox.log file if the host cache is used or not. Kind regards, Frank -- ORACLE Deutschland B.V. & Co. KG Dr.-Ing. Frank Mehnert Werkstrasse 24 Staff Engineer, VirtualBox 71384 Weinstadt, Germany mailto:[email protected] Hauptverwaltung: Riesstr. 25, D-80992 München Registergericht: Amtsgericht München, HRA 95603 Komplementärin: ORACLE Deutschland Verwaltung B.V. Rijnzathe 6, 3454PV De Meern, Niederlande Handelsregister der Handelskammer Midden-Niederlande, Nr. 30143697 Geschäftsführer: Jürgen Kunz, Marcel van de Molen, Alexander van der Ven
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