Re: [PATCH] radeon: Shrink radeon_ring_write()
From: Christian KÃnig
Date: Mon May 18 2015 - 14:11:43 EST
De-duplicating the error message is probably a good idea, but are the
remaining code changes really necessary for the size reduction?
Regards,
Christian.
On 18.05.2015 19:59, Denys Vlasenko wrote:
Inlined radeon_ring_write() has 729 callers, which amounts to about 50000
bytes of code. however, deinlining it is probably too much
of a performance impact.
This patch shrinks slow path a bit and optimizes fast path.
Comparison of generated machine code is below:
old___________________________________ new____________________________
55 push %rbp 55 push %rbp
4889e5 mov %rsp,%rbp ff4f38 decl 0x38(%rdi)
4154 push %r12 4889e5 mov %rsp,%rbp
4189f4 mov %esi,%r12d 4154 push %r12
53 push %rbx 4189f4 mov %esi,%r12d
837f3800 cmpl $0x0,0x38(%rdi) 53 push %rbx
4889fb mov %rdi,%rbx 4889fb mov %rdi,%rbx
7f0e jg <.Lbl> 7905 jns <.Lbl>
48c7c78f51a785 mov $message,%rdi
31c0 xor %eax,%eax
e89306f9ff call <drm_err> e8cbffffff call <radeon_ring_overflow>
.Lbl:
8b4328 mov 0x28(%rbx),%eax 8b5328 mov 0x28(%rbx),%edx
488b5308 mov 0x8(%rbx),%rdx 488b4308 mov 0x8(%rbx),%rax
89c1 mov %eax,%ecx 488d0490 lea (%rax,%rdx,4),%rax
ffc0 inc %eax
488d148a lea (%rdx,%rcx,4),%rdx 448920 mov %r12d,(%rax)
448922 mov %r12d,(%rdx) 8b4328 mov 0x28(%rbx),%eax
234354 and 0x54(%rbx),%eax ff4b34 decl 0x34(%rbx)
ff4b38 decl 0x38(%rbx) ffc0 inc %eax
ff4b34 decl 0x34(%rbx) 234354 and 0x54(%rbx),%eax
894328 mov %eax,0x28(%rbx) 894328 mov %eax,0x28(%rbx)
5b pop %rbx 5b pop %rbx
415c pop %r12 415c pop %r12
5d pop %rbp 5d pop %rbp
This shaves off more than 10 kbytes of code off the kernel:
text data bss dec hex filename
85657104 22294872 20627456 128579432 7a9f768 vmlinux.before
85646544 22294872 20627456 128568872 7a9ce28 vmlinux
Signed-off-by: Denys Vlasenko <dvlasenk@xxxxxxxxxx>
Cc: Christian KÃnig <christian.koenig@xxxxxxx>
Cc: Alex Deucher <alexander.deucher@xxxxxxx>
Cc: linux-kernel@xxxxxxxxxxxxxxx
---
drivers/gpu/drm/radeon/radeon.h | 11 +++++------
drivers/gpu/drm/radeon/radeon_ring.c | 5 +++++
2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index bb6b25c..9106873 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -2658,14 +2658,13 @@ void radeon_atombios_fini(struct radeon_device *rdev);
*
* Write a value to the requested ring buffer (all asics).
*/
+void radeon_ring_overflow(void);
static inline void radeon_ring_write(struct radeon_ring *ring, uint32_t v)
{
- if (ring->count_dw <= 0)
- DRM_ERROR("radeon: writing more dwords to the ring than expected!\n");
-
- ring->ring[ring->wptr++] = v;
- ring->wptr &= ring->ptr_mask;
- ring->count_dw--;
+ if (--ring->count_dw < 0)
+ radeon_ring_overflow();
+ ring->ring[ring->wptr] = v;
+ ring->wptr = (ring->wptr + 1) & ring->ptr_mask;
ring->ring_free_dw--;
}
diff --git a/drivers/gpu/drm/radeon/radeon_ring.c b/drivers/gpu/drm/radeon/radeon_ring.c
index 2456f69..8204c23 100644
--- a/drivers/gpu/drm/radeon/radeon_ring.c
+++ b/drivers/gpu/drm/radeon/radeon_ring.c
@@ -126,6 +126,11 @@ int radeon_ring_alloc(struct radeon_device *rdev, struct radeon_ring *ring, unsi
return 0;
}
+void radeon_ring_overflow(void)
+{
+ DRM_ERROR("radeon: writing more dwords to the ring than expected!\n");
+}
+
/**
* radeon_ring_lock - lock the ring and allocate space on it
*
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/