Messages in this thread | ![/](/images/icornerl.gif) | | Subject | Re: [parisc-linux] Re: Problems with kernel mmap (failing tst-mmap-eofsync in glibc on parisc) | From | James Bottomley <> | Date | 22 Aug 2003 13:41:26 -0500 |
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On Fri, 2003-08-22 at 13:34, Hugh Dickins wrote: > Might the problem be in parisc's __flush_dcache_page, > which only examines i_mmap_shared?
This is the issue: we do treat them differently.
Semantics differ between privately mapped data (where there's no coherency guarantee) and shared data (where there is). Flushing the virtual cache is expensive on pa, so we only do it for the i_mmap_shared list.
The difficulty is that a mmap of a read only file with MAP_SHARED is expecting the shared cache semantics, but gets added to the non shared list.
Since flushing the caches is a performance hog, we'd like do be able to distinguish the cases where we have to do the flush MAP_SHARED mappings from those we don't (MAP_PRIVATE).
James
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