UML - stalling during large file transfers
Encountered a baffling problem while copying large amounts of files from a archive (*.tbz) or from a remote system to a directory within a running UML system. The UML stalls while the IDE hardrive thrashes along for server minutes. It recovers, continues on with some more files, and stall again. While this is happening, all maternity's connected to that UML just freeze. The host system is perfectly accessible and on show minimal CPU usages. A running top session within the UML also show low CPU and moderate memory usage. However the UML's load increases up to 3.x for several minutes and then recovers.
System Data:
Host:
AMD Athlon 2.1Ghz running Gentoo using 2.6.9 kernel with skas3 patch. 1 SCSI 18G drive (boot drive) and one IDE 15G drive.
1G tmpfs
UML:
Vanilla 2.4.27 UML kernel (patched of UML usage)
3G file system and 512M swap.
The UML is run using 512M of mem.
The UML runs from the IDE drive.
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Quoted 12 lines · Gerhard Hannemann
Encountered a baffling problem while copying large amounts of files from a archive (*.tbz) or from a remote system to a directory within a running UML system. The UML stalls while the IDE hardrive thrashes along for server minutes. It recovers, continues on with some more files, and stall again. While this is happening, all maternity's connected to that UML just freeze.
The host system is perfectly accessible and on show minimal CPU usages. A running top session within the UML also show low CPU and moderate memory usage. However the UML's load increases up to 3.x for several minutes and then recovers.
System Data:
Quoted 9 lines
Host:
AMD Athlon 2.1Ghz running Gentoo using 2.6.9 kernel with skas3 patch. 1 SCSI 18G drive (boot drive) and one IDE 15G drive.
1G tmpfs
UML:
Vanilla 2.4.27 UML kernel (patched of UML usage)
3G file system and 512M swap.
The UML is run using 512M of mem.
The UML runs from the IDE drive.
I've just read the beginning, however I suspect you are running a not-up-to-date UML with the kernel option "CONFIG_BLK_DEV_UBD_SYNC" or the option "ubd=sync" on the command line. Until a little time ago, that meaned that the write requests (which are synchronous) were executed by the UML kernel and not by the separate thread used normally.
The workaround is to recompile disabling that option, and adding for each UBD the 's' option (i.e. ubd0= becomes ubd0s= and so on). So, you still get the safety without the slowdown.
This workaround is not needed in recent UML versions (for instance 2.6.9-bs5 is surely ok, I don't remember if stock 2.6.9 already has the fix). The fix has not yet been backported to 2.4 (although it's easy).
Signature · 14 lines
Paolo Giarrusso, aka Blaisorblade Linux registered user n. 292729 http://www.user-mode-linux.org/~blaisorblade ------------------------------------------------------- This SF.Net email is sponsored by: IntelliVIEW -- Interactive Reporting Tool for open source databases. Create drag-&-drop reports. Save time by over 75%! Publish reports on the web. Export to DOC, XLS, RTF, etc. Download a FREE copy at http://www.intelliview.com/go/osdn_nl _______________________________________________ User-mode-linux-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/user-mode-linux-devel