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authorChris Metcalf <cmetcalf@tilera.com>2013-08-15 16:29:02 -0400
committerChris Metcalf <cmetcalf@tilera.com>2013-09-03 14:53:32 -0400
commitce61cdc270a5e0dd18057bbf29bd3471abccbda8 (patch)
tree354d229299b6b02d98f40e5c650e6ddbc3411b7b /arch/tile/include
parentd7c9661115fd23b4dabb710b3080dd9919dfa891 (diff)
tile: make __write_once a synonym for __read_mostly
This was really only useful for TILE64 when we mapped the kernel data with small pages. Now we use a huge page and we really don't want to map different parts of the kernel data in different ways. We retain the __write_once name in case we want to bring it back to life at some point in the future. Note that this change uncovered a latent bug where the "smp_topology" variable happened to always be aligned mod 8 so we could store two "int" values at once, but when we eliminated __write_once it ended up only aligned mod 4. Fix with an explicit annotation. Signed-off-by: Chris Metcalf <cmetcalf@tilera.com>
Diffstat (limited to 'arch/tile/include')
-rw-r--r--arch/tile/include/asm/cache.h13
1 files changed, 10 insertions, 3 deletions
diff --git a/arch/tile/include/asm/cache.h b/arch/tile/include/asm/cache.h
index a9a529964e07..6160761d5f61 100644
--- a/arch/tile/include/asm/cache.h
+++ b/arch/tile/include/asm/cache.h
@@ -49,9 +49,16 @@
#define __read_mostly __attribute__((__section__(".data..read_mostly")))
/*
- * Attribute for data that is kept read/write coherent until the end of
- * initialization, then bumped to read/only incoherent for performance.
+ * Originally we used small TLB pages for kernel data and grouped some
+ * things together as "write once", enforcing the property at the end
+ * of initialization by making those pages read-only and non-coherent.
+ * This allowed better cache utilization since cache inclusion did not
+ * need to be maintained. However, to do this requires an extra TLB
+ * entry, which on balance is more of a performance hit than the
+ * non-coherence is a performance gain, so we now just make "read
+ * mostly" and "write once" be synonyms. We keep the attribute
+ * separate in case we change our minds at a future date.
*/
-#define __write_once __attribute__((__section__(".w1data")))
+#define __write_once __read_mostly
#endif /* _ASM_TILE_CACHE_H */