Messages in this thread | | | Date | Mon, 18 May 2015 20:11:26 +0200 | From | Christian König <> | Subject | Re: [PATCH] radeon: Shrink radeon_ring_write() |
| |
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@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 > *
| |