Messages in this thread Patch in this message | | | From | Denys Vlasenko <> | Subject | [PATCH] radeon: Shrink radeon_ring_write() | Date | Mon, 18 May 2015 19:59:15 +0200 |
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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@redhat.com> Cc: Christian König <christian.koenig@amd.com> Cc: Alex Deucher <alexander.deucher@amd.com> Cc: linux-kernel@vger.kernel.org --- 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 * -- 1.8.1.4
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