From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bali.collaboradmins.com (bali.collaboradmins.com [148.251.105.195]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 74C7D18DB37 for ; Mon, 20 Apr 2026 16:17:41 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=148.251.105.195 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776701862; cv=none; b=pheht1xxU5SsCoil1jQXpL1WIzQy0I05F3U0BUMsAkk/w4jzLpHzQ3SIUeVKzx4+/u9klfvOhtdugo5zG1GWWlsTopuEPNuN/NTUa1P/xrYpnR/vJ2Jc9FMvpAWdTpDoyDdGw10RDsmfvD+tvCmnhp+xS/Q3kZJT884EXqSsh+Y= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1776701862; c=relaxed/simple; bh=hbCGr4qqckJLAH+LL01HYy0RfcdwgCsY0WT2LD2F9OY=; h=Date:From:To:Cc:Subject:Message-ID:In-Reply-To:References: MIME-Version:Content-Type; b=p2qgODwp20sfku4XhOc/GCEs8z4R5mzweMLsn0NKkTd8Xt/+A+xQnYMrj5+IEsWCUZ15+7MGmy9TBhjDepU7PEzaC8nFqmQ4gvm+2xUnlQ8+yphow6gLJyMezPkYjHqr4r2sYfZPIliBtP6gTz3WVerNSkX64I5tpsMMxZCcZsc= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com; spf=pass smtp.mailfrom=collabora.com; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b=bv1DGRZ/; arc=none smtp.client-ip=148.251.105.195 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=collabora.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=collabora.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=collabora.com header.i=@collabora.com header.b="bv1DGRZ/" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=collabora.com; s=mail; t=1776701859; bh=hbCGr4qqckJLAH+LL01HYy0RfcdwgCsY0WT2LD2F9OY=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=bv1DGRZ/9PfOPMdFwQ5ZHvs2NkRg52Ac2/6KHD/XtluL/vSHV0Cm0z32J7oniMdvA VtnDXdcVWgA5YcXm5OVSJ3Jn5yBJrYGctXIyFwfAO7QAwLbpKbKpCUXj+vwkdFxKol ISNUJrE1w2HIuUb7Cdb+irjP1hlmLoXLqCeg+6pU0x5U7mza3CI8dxNpxpDhyiBPQO y877AE8DYs9XWKhW90VTvf7ZL4jp/BROuiUb9FldbNft20W4Bk+LVvG2ZuE4ADj9kE XGWUzVIOOZOx+ugsISe0tpj/ux1FamSzZ3ZZS2QPM262YrMSn6TVbQ388uFA8Bppsz WXLVIvuhp3a7A== Received: from fedora (unknown [100.64.0.11]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange ECDHE (prime256v1) server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) (Authenticated sender: bbrezillon) by bali.collaboradmins.com (Postfix) with ESMTPSA id 5F85817E0F7F; Mon, 20 Apr 2026 18:17:39 +0200 (CEST) Date: Mon, 20 Apr 2026 18:17:35 +0200 From: Boris Brezillon To: Nicolas Frattaroli Cc: Maarten Lankhorst , Maxime Ripard , Thomas Zimmermann , David Airlie , Simona Vetter , Steven Price , Liviu Dudau , dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org, kernel@collabora.com Subject: Re: [PATCH 2/2] drm/panthor: Implement evicted status for GEM objects Message-ID: <20260420181735.2990999e@fedora> In-Reply-To: <20260420-panthor-bo-reclaim-observability-v1-2-a4d1a36ee84f@collabora.com> References: <20260420-panthor-bo-reclaim-observability-v1-0-a4d1a36ee84f@collabora.com> <20260420-panthor-bo-reclaim-observability-v1-2-a4d1a36ee84f@collabora.com> Organization: Collabora X-Mailer: Claws Mail 4.4.0 (GTK 3.24.52; x86_64-redhat-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 20 Apr 2026 17:47:00 +0200 Nicolas Frattaroli wrote: > For fdinfo to be able to fill its evicted counter with data, panthor > needs to keep track of whether a GEM object has ever been reclaimed. > Just checking whether the pages are resident isn't enough, as newly > allocated objects also won't be resident. > > Do this with a new atomic_t member on panthor_gem_object. It's increased > when an object gets evicted by the shrinker. While it's allowed to wrap > around to below zero and assume a value less than a previous observed > value, the reclaim counter will never return to 0 for any particular > object once it's been reclaimed at least once. > > Use this new member to then set the appropriate DRM_GEM_OBJECT_EVICTED > status flag for fdinfo, and use it in the gems debugfs. It's possible to > distinguish evicted non-resident pages from newly allocated non-resident > pages by checking whether reclaimed_count is != 0. > > Signed-off-by: Nicolas Frattaroli > --- > drivers/gpu/drm/panthor/panthor_gem.c | 10 ++++++++++ > drivers/gpu/drm/panthor/panthor_gem.h | 11 +++++++++++ > 2 files changed, 21 insertions(+) > > diff --git a/drivers/gpu/drm/panthor/panthor_gem.c b/drivers/gpu/drm/panthor/panthor_gem.c > index 69cef05b6ef7..4b761b39565d 100644 > --- a/drivers/gpu/drm/panthor/panthor_gem.c > +++ b/drivers/gpu/drm/panthor/panthor_gem.c > @@ -687,6 +687,10 @@ static void panthor_gem_evict_locked(struct panthor_gem_object *bo) > if (drm_WARN_ON_ONCE(bo->base.dev, !bo->backing.pages)) > return; > > + /* Don't ever wrap around as far as 0, jump from INT_MIN to 1 */ > + if (!atomic_inc_unless_negative(&bo->reclaimed_count)) > + atomic_set(&bo->reclaimed_count, 1); Can't we just go atomic_add_unless(&bo->reclaimed_count, 1, INT_MAX); here, to handle the INT_MAX saturation? > + > panthor_gem_dev_map_cleanup_locked(bo); > panthor_gem_backing_cleanup_locked(bo); > panthor_gem_update_reclaim_state_locked(bo, NULL); > @@ -788,6 +792,8 @@ static enum drm_gem_object_status panthor_gem_status(struct drm_gem_object *obj) > > if (drm_gem_is_imported(&bo->base) || bo->backing.pages) > res |= DRM_GEM_OBJECT_RESIDENT; > + else if (atomic_read(&bo->reclaimed_count)) > + res |= DRM_GEM_OBJECT_EVICTED; > > return res; > } > @@ -1595,6 +1601,7 @@ static void panthor_gem_debugfs_print_flag_names(struct seq_file *m) > static const char * const gem_state_flags_names[] = { > [PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT] = "imported", > [PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT] = "exported", > + [PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT] = "evicted", > }; > > static const char * const gem_usage_flags_names[] = { > @@ -1648,6 +1655,9 @@ static void panthor_gem_debugfs_bo_print(struct panthor_gem_object *bo, > > if (drm_gem_is_imported(&bo->base)) > gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED; > + else if (!resident_size && atomic_read(&bo->reclaimed_count)) > + gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED; I think it'd be interesting to know the number of times a BO got evicted. > + > if (bo->base.dma_buf) > gem_state_flags |= PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED; > > diff --git a/drivers/gpu/drm/panthor/panthor_gem.h b/drivers/gpu/drm/panthor/panthor_gem.h > index ae0491d0b121..1ab573f03330 100644 > --- a/drivers/gpu/drm/panthor/panthor_gem.h > +++ b/drivers/gpu/drm/panthor/panthor_gem.h > @@ -19,12 +19,16 @@ struct panthor_vm; > enum panthor_debugfs_gem_state_flags { > PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT = 0, > PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT = 1, > + PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT = 2, > > /** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED: GEM BO is PRIME imported. */ > PANTHOR_DEBUGFS_GEM_STATE_FLAG_IMPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_IMPORTED_BIT), > > /** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED: GEM BO is PRIME exported. */ > PANTHOR_DEBUGFS_GEM_STATE_FLAG_EXPORTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EXPORTED_BIT), > + > + /** @PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED: GEM BO is evicted to swap. */ > + PANTHOR_DEBUGFS_GEM_STATE_FLAG_EVICTED = BIT(PANTHOR_DEBUGFS_GEM_STATE_EVICTED_BIT), > }; > > enum panthor_debugfs_gem_usage_flags { > @@ -172,6 +176,13 @@ struct panthor_gem_object { > /** @reclaim_state: Cached reclaim state */ > enum panthor_gem_reclaim_state reclaim_state; > > + /** > + * @reclaimed_count: How many times object has been evicted to swap. * > + * Never returns to 0 once incremented even on wrap-around, but may > + * become < 0 and < the previous value if wrap-around occurs. With the saturation I suggested, I'd just add that when INT_MAX is reached, it will stay there. > + */ > + atomic_t reclaimed_count; > + > /** > * @exclusive_vm_root_gem: Root GEM of the exclusive VM this GEM object > * is attached to. >