Messages in this thread | | | Date | Wed, 26 May 1999 09:44:07 +0200 | From | Jakub Jelinek <> | Subject | Re: [PATCH] cache large files in the page cache |
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> Details: > > This patch replaces vm_offset with vm_index, with the relationship: > vm_offset == (vm_index << PAGE_SHIFT). Except vm_index can hold larger > offsets.
I have minor suggestion to the patch. Instead of using vm_index << PAGE_SHIFT and page->key << PAGE_CACHE_SHIFT shifts either choose different constant names for this shifting (VM_INDEX_SHIFT and PAGE_KEY_SHIFT) or hide these shifts by some pretty macros (you'll need two for each for both directions in that case - if you go the macro way, maybe it would be a good idea to make vm_index and key type some structure with a single member like mm_segment_t for more strict typechecking). This would have the advantage of avoiding shifting on 64bit archs, where it really is not necessary as no filesystem will support 16000EB filesizes in the near future. I know shifts are not expensive, on the other side count how many there will be and IMHO it should be considered. It could make the code more readable at the same time. VM_INDEX_SHIFT would be defined to 0 on alpha,sparc64 (merced,mips64,ppc64) and PAGE_SHIFT on other platforms. The same with PAGE_KEY_SHIFT.
Cheers, Jakub ___________________________________________________________________ Jakub Jelinek | jj@sunsite.mff.cuni.cz | http://sunsite.mff.cuni.cz Administrator of SunSITE Czech Republic, MFF, Charles University ___________________________________________________________________ UltraLinux | http://ultra.linux.cz/ | http://ultra.penguin.cz/ Linux version 2.3.3 on a sparc64 machine (1343.49 BogoMips) ___________________________________________________________________
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