[PATCH v2] drm/xe: Defer buffer object shrinker write-backs and GPU waits
Thomas Hellström
thomas.hellstrom at linux.intel.com
Tue Aug 5 07:48:42 UTC 2025
When the xe buffer-object shrinker allows GPU waits and write-back,
(typically from kswapd), perform multiple passes, skipping
subsequent passes if the shrinker number of scanned objects target
is reached.
1) Without GPU waits and write-back
2) Without write-back
3) With both GPU-waits and write-back
This is to avoid stalls and costly write- and readbacks unless they
are really necessary.
v2:
- Don't test for scan completion twice. (Stuart Summers)
- Update tags.
Reported-by: melvyn <melvyn2 at dnsense.pub>
Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5557
Cc: Summers Stuart <stuart.summers at intel.com>
Fixes: 00c8efc3180f ("drm/xe: Add a shrinker for xe bos")
Cc: <stable at vger.kernel.org> # v6.15+
Signed-off-by: Thomas Hellström <thomas.hellstrom at linux.intel.com>
---
drivers/gpu/drm/xe/xe_shrinker.c | 51 +++++++++++++++++++++++++++++---
1 file changed, 47 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/xe/xe_shrinker.c b/drivers/gpu/drm/xe/xe_shrinker.c
index 1c3c04d52f55..90244fe59b59 100644
--- a/drivers/gpu/drm/xe/xe_shrinker.c
+++ b/drivers/gpu/drm/xe/xe_shrinker.c
@@ -54,10 +54,10 @@ xe_shrinker_mod_pages(struct xe_shrinker *shrinker, long shrinkable, long purgea
write_unlock(&shrinker->lock);
}
-static s64 xe_shrinker_walk(struct xe_device *xe,
- struct ttm_operation_ctx *ctx,
- const struct xe_bo_shrink_flags flags,
- unsigned long to_scan, unsigned long *scanned)
+static s64 __xe_shrinker_walk(struct xe_device *xe,
+ struct ttm_operation_ctx *ctx,
+ const struct xe_bo_shrink_flags flags,
+ unsigned long to_scan, unsigned long *scanned)
{
unsigned int mem_type;
s64 freed = 0, lret;
@@ -93,6 +93,48 @@ static s64 xe_shrinker_walk(struct xe_device *xe,
return freed;
}
+/*
+ * Try shrinking idle objects without writeback first, then if not sufficient,
+ * try also non-idle objects and finally if that's not sufficient either,
+ * add writeback. This avoids stalls and explicit writebacks with light or
+ * moderate memory pressure.
+ */
+static s64 xe_shrinker_walk(struct xe_device *xe,
+ struct ttm_operation_ctx *ctx,
+ const struct xe_bo_shrink_flags flags,
+ unsigned long to_scan, unsigned long *scanned)
+{
+ bool no_wait_gpu = true;
+ struct xe_bo_shrink_flags save_flags = flags;
+ s64 lret, freed;
+
+ swap(no_wait_gpu, ctx->no_wait_gpu);
+ save_flags.writeback = false;
+ lret = __xe_shrinker_walk(xe, ctx, save_flags, to_scan, scanned);
+ swap(no_wait_gpu, ctx->no_wait_gpu);
+ if (lret < 0 || *scanned >= to_scan)
+ return lret;
+
+ freed = lret;
+ if (!ctx->no_wait_gpu) {
+ lret = __xe_shrinker_walk(xe, ctx, save_flags, to_scan, scanned);
+ if (lret < 0)
+ return lret;
+ freed += lret;
+ if (*scanned >= to_scan)
+ return freed;
+ }
+
+ if (flags.writeback) {
+ lret = __xe_shrinker_walk(xe, ctx, flags, to_scan, scanned);
+ if (lret < 0)
+ return lret;
+ freed += lret;
+ }
+
+ return freed;
+}
+
static unsigned long
xe_shrinker_count(struct shrinker *shrink, struct shrink_control *sc)
{
@@ -199,6 +241,7 @@ static unsigned long xe_shrinker_scan(struct shrinker *shrink, struct shrink_con
runtime_pm = xe_shrinker_runtime_pm_get(shrinker, true, 0, can_backup);
shrink_flags.purge = false;
+
lret = xe_shrinker_walk(shrinker->xe, &ctx, shrink_flags,
nr_to_scan, &nr_scanned);
if (lret >= 0)
--
2.50.1
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