Re: [PATCH] powerpc: book3e_64: fix the align size for paca_struct
On Mon, Mar 09, 2015 at 06:31:25PM +1100, Benjamin Herrenschmidt wrote: On Mon, 2015-03-09 at 09:13 +0800, Kevin Hao wrote: On Sun, Mar 08, 2015 at 08:13:26PM +1100, Benjamin Herrenschmidt wrote: On Sat, 2015-03-07 at 19:14 +0800, Kevin Hao wrote: All the cache line size of the current book3e 64bit SoCs are 64 bytes. So we should use this size to align the member of paca_struct. With this change we save 192 bytes. Also change it to __aligned(size) since it is preferred over __attribute__((aligned(size))). Why should we favor the book3e CPUs over the book3s ones ? Why do you think so? This only change the align size of the paca_struct's members which are private to book3e CPUs, and should not have any effect to book3s ones. Did I miss something? No, your explanation was lacking that important detail :-) Sorry for the confusion, I will add this information in the commit log. Thanks, Kevin pgpNhzA4BHwp3.pgp Description: PGP signature ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH] powerpc: book3e_64: fix the align size for paca_struct
On Mon, 2015-03-09 at 09:13 +0800, Kevin Hao wrote: On Sun, Mar 08, 2015 at 08:13:26PM +1100, Benjamin Herrenschmidt wrote: On Sat, 2015-03-07 at 19:14 +0800, Kevin Hao wrote: All the cache line size of the current book3e 64bit SoCs are 64 bytes. So we should use this size to align the member of paca_struct. With this change we save 192 bytes. Also change it to __aligned(size) since it is preferred over __attribute__((aligned(size))). Why should we favor the book3e CPUs over the book3s ones ? Why do you think so? This only change the align size of the paca_struct's members which are private to book3e CPUs, and should not have any effect to book3s ones. Did I miss something? No, your explanation was lacking that important detail :-) Thanks, Kevin ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [PATCH] powerpc: book3e_64: fix the align size for paca_struct
On Sat, 2015-03-07 at 19:14 +0800, Kevin Hao wrote:
All the cache line size of the current book3e 64bit SoCs are 64 bytes.
So we should use this size to align the member of paca_struct.
With this change we save 192 bytes. Also change it to __aligned(size)
since it is preferred over __attribute__((aligned(size))).
Why should we favor the book3e CPUs over the book3s ones ? Since we
can't build a kernel that deals with both, make it a compile option.
Before:
/* size: 1920, cachelines: 30, members: 46 */
/* sum members: 1667, holes: 6, sum holes: 141 */
/* padding: 112 */
After:
/* size: 1728, cachelines: 27, members: 46 */
/* sum members: 1667, holes: 4, sum holes: 13 */
/* padding: 48 */
Signed-off-by: Kevin Hao haoke...@gmail.com
---
arch/powerpc/include/asm/paca.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index e5f22c6c4bf9..70bd4381f8e6 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -106,9 +106,9 @@ struct paca_struct {
#endif /* CONFIG_PPC_STD_MMU_64 */
#ifdef CONFIG_PPC_BOOK3E
- u64 exgen[8] __attribute__((aligned(0x80)));
+ u64 exgen[8] __aligned(0x40);
/* Keep pgd in the same cacheline as the start of extlb */
- pgd_t *pgd __attribute__((aligned(0x80))); /* Current PGD */
+ pgd_t *pgd __aligned(0x40); /* Current PGD */
pgd_t *kernel_pgd; /* Kernel PGD */
/* Shared by all threads of a core -- points to tcd of first thread */
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Re: [PATCH] powerpc: book3e_64: fix the align size for paca_struct
On Sun, Mar 08, 2015 at 08:13:26PM +1100, Benjamin Herrenschmidt wrote: On Sat, 2015-03-07 at 19:14 +0800, Kevin Hao wrote: All the cache line size of the current book3e 64bit SoCs are 64 bytes. So we should use this size to align the member of paca_struct. With this change we save 192 bytes. Also change it to __aligned(size) since it is preferred over __attribute__((aligned(size))). Why should we favor the book3e CPUs over the book3s ones ? Why do you think so? This only change the align size of the paca_struct's members which are private to book3e CPUs, and should not have any effect to book3s ones. Did I miss something? Thanks, Kevin pgpx9Vdlqxujn.pgp Description: PGP signature ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[PATCH] powerpc: book3e_64: fix the align size for paca_struct
All the cache line size of the current book3e 64bit SoCs are 64 bytes.
So we should use this size to align the member of paca_struct.
With this change we save 192 bytes. Also change it to __aligned(size)
since it is preferred over __attribute__((aligned(size))).
Before:
/* size: 1920, cachelines: 30, members: 46 */
/* sum members: 1667, holes: 6, sum holes: 141 */
/* padding: 112 */
After:
/* size: 1728, cachelines: 27, members: 46 */
/* sum members: 1667, holes: 4, sum holes: 13 */
/* padding: 48 */
Signed-off-by: Kevin Hao haoke...@gmail.com
---
arch/powerpc/include/asm/paca.h | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/arch/powerpc/include/asm/paca.h b/arch/powerpc/include/asm/paca.h
index e5f22c6c4bf9..70bd4381f8e6 100644
--- a/arch/powerpc/include/asm/paca.h
+++ b/arch/powerpc/include/asm/paca.h
@@ -106,9 +106,9 @@ struct paca_struct {
#endif /* CONFIG_PPC_STD_MMU_64 */
#ifdef CONFIG_PPC_BOOK3E
- u64 exgen[8] __attribute__((aligned(0x80)));
+ u64 exgen[8] __aligned(0x40);
/* Keep pgd in the same cacheline as the start of extlb */
- pgd_t *pgd __attribute__((aligned(0x80))); /* Current PGD */
+ pgd_t *pgd __aligned(0x40); /* Current PGD */
pgd_t *kernel_pgd; /* Kernel PGD */
/* Shared by all threads of a core -- points to tcd of first thread */
--
2.1.0
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