On 04/22/2014 01:16 PM, chru...@suse.cz wrote: > Hi! >> I observe that mmap_11-4 fails in my x86 environment with: >> >> Test FAILED: Modification of the partial page at the end of an object is >> written out > > I've seen some failures lately too but haven't had time to look into > these yet. > >> I did some googling and found that you rose this problem in 2012: >> http://linux-kernel.2935.n7.nabble.com/Partialy-mapped-page-stays-in-page-cache-after-unmap-td379857.html >> >> I'm interested what you meant in your patch for the mmap's manual page >> by "In some cases, this could be fixed by calling msync(2) before the >> unmap takes place;" >> >> What are these "some cases"? > > That depends on whether is the mmaped file backed up by a disk based > filesystem or not. > > Mapped pages are stored in a cache, so if you modify content of a page > that is beyond the mapping but inside the last page the data stays there > till they are written back to the disk and reloaded into the cache > (which can be forced by the msync()). For memory backed filesystems > (tmpfs etc) msync() is no-op because there is no permanent storage to > write the data to, so the rest of partial page is never cleared. > >> I took your test program from the man thread and executed it on KVM and >> on an Sun Ultra 45. >> >> Here are the results: >> >> 1. Debian 7 + KVM + 3.2.0-4-amd64 >> * without msync() it fails >> * with msync() it fails >> >> 2. Debian 7 + Ultra + 3.2.0-4-sparc64-smp >> * without msync() it fails >> * with msync() it passes (!!!) >> >> So it looks like msync() on x86 doesn't help us. The question here if >> it's a linux+x86 bug or not... > > Is the /tmp/ filesystem the same?
yes, ext4 in both cases. > >> Could you check your test program and mmap_11-4 in your environment? > > Added to my TODO but I'm not sure if I can get to this till the end of > the week. > ------------------------------------------------------------------------------ Start Your Social Network Today - Download eXo Platform Build your Enterprise Intranet with eXo Platform Software Java Based Open Source Intranet - Social, Extensible, Cloud Ready Get Started Now And Turn Your Intranet Into A Collaboration Platform http://p.sf.net/sfu/ExoPlatform _______________________________________________ Ltp-list mailing list Ltp-list@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/ltp-list
