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authorgraham.gower@gmail.com <graham.gower@gmail.com@e8e0d7a0-c8d9-11dd-a880-a1081c7ac358>2011-02-17 19:02:14 (EST)
committer graham.gower@gmail.com <graham.gower@gmail.com@e8e0d7a0-c8d9-11dd-a880-a1081c7ac358>2011-02-17 19:02:14 (EST)
commit4510dc50d303256dd5f74681119c826c329f6939 (patch)
tree9442ed642e0f1a632d53ebcfa253ef956db3259f /libbb/unarchive.c
parentf5072b06fadc446ce4579ac6c8b0b9bfa3d55625 (diff)
Allow vfork()ing an external gunzip binary instead of using fork().
Patch from Mike Westerhof, with minor modifications to allow the use of both GNU gunzip and busybox gunzip. His original patch header follows. This patch allows a user to set an environment variable to cause opkg to select either the built-in gunzip code or an external gunzip utility, in order to dodge the OOM Killer. The built-in code is, of course, is the most desirable way to use opkg, since it is far more efficient. However, the built-in code can trigger the OOM (out of memory) killer on small-memory machines, like the 32MB NSLU2. This occurs because a standard fork will duplicate the entire address space of the parent. Since opkg reads the entire feed database into memory, this problem is compounded by large feeds. This patch introduces a means for the user to cause opkg to use vfork() instead -- vfork() does not behave in the same manner as fork(), and does not trigger the OOM killer. However, the semantics of vfork() are such that it cannot run the built-in gunzip code. Instead, it must exec() an external utility to perform the gunzip operation. It seems counter-intuitive, but the vfork()/exec() approach is the only good way to avoid triggering the dreaded OOM killer. In order to use this, the user must manually set the OPKG_USE_VFORK environment variable to any value. For example: $ OPKG_USE_VFORK=1 opkg install samba The external utility used to do the gunzip operation is "busybox gunzip". It would have been nice to be able to just invoke "gunzip", but the full gunzip executable behaves slightly differently than does busybox, generating annoying warning messages. This is an update of the original patch by Mike Westerhof, Dec 2008. Mike Westerhof, Feb 2011 git-svn-id: http://opkg.googlecode.com/svn/trunk@604 e8e0d7a0-c8d9-11dd-a880-a1081c7ac358
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