[PATCH] drm/xe: Defer buffer object shrinker write-backs and GPU waits
Summers, Stuart
stuart.summers at intel.com
Mon Aug 4 19:29:46 UTC 2025
On Mon, 2025-08-04 at 10:10 +0200, Thomas Hellström wrote:
> When the xe buffer-object shrinker allows GPU waits and write-back,
> (typically from kswapd), perform multilpe passes, skipping
/s/multilpe/multiple/
> 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.
>
> Closes:
> https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/5557#note_3035136
> 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>
I see the reported requested:
Reported-by: melvyn <melvyn2 at dnsense.pub>
> ---
> 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..bc3439bd4450 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)
Why not include this in the !ctx->no_wait_gpu condition above? If ctx-
>no_wait_gpu was passed in as true here, we're just checking scanned >=
to_scan twice in a row with the same values.
Otherwise the patch lgtm.
Thanks,
Stuart
> + 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)
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