Messages in this thread Patch in this message | | | From | Mike Frysinger <> | Date | Sat, 28 Nov 2009 10:40:30 -0500 | Subject | avoiding duplicate icache flushing of shared maps on nommu |
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when working with FDPIC, there are many shared maps of read only text regions (the C library, applet packages like busybox, ...) between applications. but the current mm/nommu.c:do_mmap_pgoff() function will issue an icache flush whenever a vma is added to a mm instead of only doing it when the map is initially created. am i missing something obvious here, or would a change like below be OK ? this easily cuts the number of icache flushes during boot by 50% if not more.
(yes, this now does the icache flush while holding the nommu_region_sem, but i'm interested if the _idea_ is OK)
--- a/mm/nommu.c +++ b/mm/nommu.c @@ -1409,14 +1409,14 @@ unsigned long do_mmap_pgoff(struct file *file,
current->mm->total_vm += len >> PAGE_SHIFT;
+ if (prot & PROT_EXEC) + flush_icache_range(result, result + len); + share: add_vma_to_mm(current->mm, vma);
up_write(&nommu_region_sem);
- if (prot & PROT_EXEC) - flush_icache_range(result, result + len); - kleave(" = %lx", result); return result;
-mike
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