return ret;
}
-/* Returns how many bytes TTM can move per IB.
+/* Convert microseconds to bytes. */
+static u64 us_to_bytes(struct amdgpu_device *adev, s64 us)
+{
+ if (us <= 0 || !adev->mm_stats.log2_max_MBps)
+ return 0;
+
+ /* Since accum_us is incremented by a million per second, just
+ * multiply it by the number of MB/s to get the number of bytes.
+ */
+ return us << adev->mm_stats.log2_max_MBps;
+}
+
+static s64 bytes_to_us(struct amdgpu_device *adev, u64 bytes)
+{
+ if (!adev->mm_stats.log2_max_MBps)
+ return 0;
+
+ return bytes >> adev->mm_stats.log2_max_MBps;
+}
+
+/* Returns how many bytes TTM can move right now. If no bytes can be moved,
+ * it returns 0. If it returns non-zero, it's OK to move at least one buffer,
+ * which means it can go over the threshold once. If that happens, the driver
+ * will be in debt and no other buffer migrations can be done until that debt
+ * is repaid.
+ *
+ * This approach allows moving a buffer of any size (it's important to allow
+ * that).
+ *
+ * The currency is simply time in microseconds and it increases as the clock
+ * ticks. The accumulated microseconds (us) are converted to bytes and
+ * returned.
*/
static u64 amdgpu_cs_get_threshold_for_moves(struct amdgpu_device *adev)
{
- u64 real_vram_size = adev->mc.real_vram_size;
- u64 vram_usage = atomic64_read(&adev->vram_usage);
+ s64 time_us, increment_us;
+ u64 max_bytes;
+ u64 free_vram, total_vram, used_vram;
- /* This function is based on the current VRAM usage.
+ /* Allow a maximum of 200 accumulated ms. This is basically per-IB
+ * throttling.
*
- * - If all of VRAM is free, allow relocating the number of bytes that
- * is equal to 1/4 of the size of VRAM for this IB.
+ * It means that in order to get full max MBps, at least 5 IBs per
+ * second must be submitted and not more than 200ms apart from each
+ * other.
+ */
+ const s64 us_upper_bound = 200000;
- * - If more than one half of VRAM is occupied, only allow relocating
- * 1 MB of data for this IB.
- *
- * - From 0 to one half of used VRAM, the threshold decreases
- * linearly.
- * __________________
- * 1/4 of -|\ |
- * VRAM | \ |
- * | \ |
- * | \ |
- * | \ |
- * | \ |
- * | \ |
- * | \________|1 MB
- * |----------------|
- * VRAM 0 % 100 %
- * used used
- *
- * Note: It's a threshold, not a limit. The threshold must be crossed
- * for buffer relocations to stop, so any buffer of an arbitrary size
- * can be moved as long as the threshold isn't crossed before
- * the relocation takes place. We don't want to disable buffer
- * relocations completely.
+ if (!adev->mm_stats.log2_max_MBps)
+ return 0;
+
+ total_vram = adev->mc.real_vram_size - adev->vram_pin_size;
+ used_vram = atomic64_read(&adev->vram_usage);
+ free_vram = used_vram >= total_vram ? 0 : total_vram - used_vram;
+
+ spin_lock(&adev->mm_stats.lock);
+
+ /* Increase the amount of accumulated us. */
+ time_us = ktime_to_us(ktime_get());
+ increment_us = time_us - adev->mm_stats.last_update_us;
+ adev->mm_stats.last_update_us = time_us;
+ adev->mm_stats.accum_us = min(adev->mm_stats.accum_us + increment_us,
+ us_upper_bound);
+
+ /* This prevents the short period of low performance when the VRAM
+ * usage is low and the driver is in debt or doesn't have enough
+ * accumulated us to fill VRAM quickly.
*
- * The idea is that buffers should be placed in VRAM at creation time
- * and TTM should only do a minimum number of relocations during
- * command submission. In practice, you need to submit at least
- * a dozen IBs to move all buffers to VRAM if they are in GTT.
+ * The situation can occur in these cases:
+ * - a lot of VRAM is freed by userspace
+ * - the presence of a big buffer causes a lot of evictions
+ * (solution: split buffers into smaller ones)
*
- * Also, things can get pretty crazy under memory pressure and actual
- * VRAM usage can change a lot, so playing safe even at 50% does
- * consistently increase performance.
+ * If 128 MB or 1/8th of VRAM is free, start filling it now by setting
+ * accum_us to a positive number.
*/
+ if (free_vram >= 128 * 1024 * 1024 || free_vram >= total_vram / 8) {
+ s64 min_us;
+
+ /* Be more aggresive on dGPUs. Try to fill a portion of free
+ * VRAM now.
+ */
+ if (!(adev->flags & AMD_IS_APU))
+ min_us = bytes_to_us(adev, free_vram / 4);
+ else
+ min_us = 0; /* Reset accum_us on APUs. */
+
+ adev->mm_stats.accum_us = max(min_us, adev->mm_stats.accum_us);
+ }
- u64 half_vram = real_vram_size >> 1;
- u64 half_free_vram = vram_usage >= half_vram ? 0 : half_vram - vram_usage;
- u64 bytes_moved_threshold = half_free_vram >> 1;
- return max(bytes_moved_threshold, 1024*1024ull);
+ /* This returns 0 if the driver is in debt to disallow (optional)
+ * buffer moves.
+ */
+ max_bytes = us_to_bytes(adev, adev->mm_stats.accum_us);
+
+ spin_unlock(&adev->mm_stats.lock);
+ return max_bytes;
+}
+
+/* Report how many bytes have really been moved for the last command
+ * submission. This can result in a debt that can stop buffer migrations
+ * temporarily.
+ */
+static void amdgpu_cs_report_moved_bytes(struct amdgpu_device *adev,
+ u64 num_bytes)
+{
+ spin_lock(&adev->mm_stats.lock);
+ adev->mm_stats.accum_us -= bytes_to_us(adev, num_bytes);
+ spin_unlock(&adev->mm_stats.lock);
}
static int amdgpu_cs_bo_validate(struct amdgpu_cs_parser *p,
if (bo->pin_count)
return 0;
- /* Avoid moving this one if we have moved too many buffers
- * for this IB already.
- *
- * Note that this allows moving at least one buffer of
- * any size, because it doesn't take the current "bo"
- * into account. We don't want to disallow buffer moves
- * completely.
+ /* Don't move this buffer if we have depleted our allowance
+ * to move it. Don't move anything if the threshold is zero.
*/
- if (p->bytes_moved <= p->bytes_moved_threshold)
+ if (p->bytes_moved < p->bytes_moved_threshold)
domain = bo->prefered_domains;
else
domain = bo->allowed_domains;
goto error_validate;
}
+ amdgpu_cs_report_moved_bytes(p->adev, p->bytes_moved);
+
fpriv->vm.last_eviction_counter =
atomic64_read(&p->adev->num_evictions);
projects / GitHub / moto-9609 / android_kernel_motorola_exynos9610.git / commitdiff