[Spice-devel] [spice-gtk PATCH v2] This adds reference counting to cached images.
Sandy Stutsman
sstutsma at redhat.com
Thu Jun 25 07:17:09 PDT 2015
Hi.
----- Original Message -----
> From: "Fabiano Fidêncio" <fabiano at fidencio.org>
> To: "Sandy Stutsman" <sstutsma at redhat.com>
> Cc: spice-devel at lists.freedesktop.org
> Sent: Thursday, June 25, 2015 6:50:11 AM
> Subject: Re: [Spice-devel] [spice-gtk PATCH v2] This adds reference counting to cached images.
>
> On Wed, Jun 24, 2015 at 7:09 PM, Sandy Stutsman <sstutsma at redhat.com> wrote:
> >
> > Windows guests with multi-monitors will often send down the same image
> > via different channels. If these instances are not counted, one channel
> > can delete an image before all the rest of the channels are finished with
> > it. In this case, the client will hang.
> >
> > This can happen, for instance, when the Windows guest is updating the
> > monitor's wallpaper. There is a driver instance for each monitor, so each
> > one is sending down its own copy of the same image with the same id. As
> > one channel may be busier than another, the order that the client executes
> > commands may not be the same order as the server issued them. Here's what
> > can happen:
> >
> > On the server side:
> > Monitor 1 sends image A
> > Monitor 1 sends multiple rendering commands for image A
> > Monitor 1 removes image A
> > Monitor 2 sends image A
> > Monitor 2 sends rendering commands for image A
> > On the client side:
> > Monitor 1 adds image A to the cache
> > Monitor 1 starts rendering with image A
> > Monitor 2 adds image A to the cache - has same id, so image is replaced
> > Monitor 1 removes image A - image A is completely removed from cache
> > Monitor 2 render command hangs waiting for image A
> >
> > Addresses bug: https://bugzilla.redhat.com/show_bug.cgi?id=1194354
> > ---
> > Change since v1
> > *Add to commit log
> > ---
> > src/spice-channel-cache.h | 60
> > ++++++++++++++++++++++++++++++++++++-----------
> > src/spice-session.c | 2 +-
> > 2 files changed, 47 insertions(+), 15 deletions(-)
> >
> > diff --git a/src/spice-channel-cache.h b/src/spice-channel-cache.h
> > index 17775e6..968e661 100644
> > --- a/src/spice-channel-cache.h
> > +++ b/src/spice-channel-cache.h
> > @@ -27,15 +27,20 @@ G_BEGIN_DECLS
> > typedef struct display_cache_item {
> > guint64 id;
> > gboolean lossy;
> > + uint32_t ref_count;
>
> Could be guint32, right?
Yep.
>
> > } display_cache_item;
> >
> > -typedef GHashTable display_cache;
> > +typedef struct display_cache {
> > + GHashTable *table;
> > + gboolean ref_counted;
> > +}display_cache;
> >
> > static inline display_cache_item* cache_item_new(guint64 id, gboolean
> > lossy)
> > {
> > display_cache_item *self = g_slice_new(display_cache_item);
> > self->id = id;
> > self->lossy = lossy;
> > + self->ref_count = 1;
> > return self;
> > }
> >
> > @@ -46,18 +51,24 @@ static inline void cache_item_free(display_cache_item
> > *self)
> >
> > static inline display_cache* cache_new(GDestroyNotify value_destroy)
> > {
> > - GHashTable* self;
> > -
> > - self = g_hash_table_new_full(g_int64_hash, g_int64_equal,
> > - (GDestroyNotify)cache_item_free,
> > - value_destroy);
> > -
> > + display_cache * self = g_slice_new(display_cache);
> > + self->table = g_hash_table_new_full(g_int64_hash, g_int64_equal,
> > + (GDestroyNotify) cache_item_free,
> > + value_destroy);
> > + self->ref_counted = FALSE;
> > return self;
> > }
> >
> > +static inline display_cache * cache_image_new(GDestroyNotify
> > value_destroy)
> > +{
> > + display_cache * self = cache_new(value_destroy);
> > + self->ref_counted = TRUE;
> > + return self;
> > +};
> > +
> > static inline gpointer cache_find(display_cache *cache, uint64_t id)
> > {
> > - return g_hash_table_lookup(cache, &id);
> > + return g_hash_table_lookup(cache->table, &id);
> > }
> >
> > static inline gpointer cache_find_lossy(display_cache *cache, uint64_t id,
> > gboolean *lossy)
> > @@ -65,7 +76,7 @@ static inline gpointer cache_find_lossy(display_cache
> > *cache, uint64_t id, gbool
> > gpointer value;
> > display_cache_item *item;
> >
> > - if (!g_hash_table_lookup_extended(cache, &id, (gpointer*)&item,
> > &value))
> > + if (!g_hash_table_lookup_extended(cache->table, &id, (gpointer*)&item,
> > &value))
> > return NULL;
> >
> > *lossy = item->lossy;
> > @@ -77,8 +88,17 @@ static inline void cache_add_lossy(display_cache *cache,
> > uint64_t id,
> > gpointer value, gboolean lossy)
> > {
> > display_cache_item *item = cache_item_new(id, lossy);
> > -
> > - g_hash_table_replace(cache, item, value);
> > + display_cache_item *current_item;
> > + gpointer current_image;
> > +
> > + //If image is currently in the table add its reference count before
> > replacing it
> > + if(cache->ref_counted) {
> > + if(g_hash_table_lookup_extended(cache->table, &id, (gpointer*)
> > ¤t_item,
> > + (gpointer*) ¤t_image)) {
> > + item->ref_count = current_item->ref_count + 1;
> > + }
> > + }
> > + g_hash_table_replace(cache->table, item, value);
> > }
> >
> > static inline void cache_add(display_cache *cache, uint64_t id, gpointer
> > value)
> > @@ -88,17 +108,29 @@ static inline void cache_add(display_cache *cache,
> > uint64_t id, gpointer value)
> >
> > static inline gboolean cache_remove(display_cache *cache, uint64_t id)
> > {
> > - return g_hash_table_remove(cache, &id);
> > + display_cache_item * item;
> > + gpointer value;
> > +
> > + if( g_hash_table_lookup_extended(cache->table, &id, (gpointer*) &item,
> > &value)) {
> > + --item->ref_count;
> > + if(!cache->ref_counted || !item->ref_count ) {
>
> I really would prefer to have comparisons (when not booleans) in the
> explicit way, like:
> if(!cache->ref_counted || item->ref_count > 0) { ... }
>
actually changed to if(!cache->ref_counted || item->ref_count == 0) { ... }
> > + return g_hash_table_remove(cache->table, &id);
> > + }
> > + }
> > + else {
> > + return FALSE;
> > + }
> > + return TRUE;
> > }
> >
> > static inline void cache_clear(display_cache *cache)
> > {
> > - g_hash_table_remove_all(cache);
> > + g_hash_table_remove_all(cache->table);
> > }
> >
> > static inline void cache_unref(display_cache *cache)
> > {
> > - g_hash_table_unref(cache);
> > + g_hash_table_unref(cache->table);
> > }
> >
> > G_END_DECLS
> > diff --git a/src/spice-session.c b/src/spice-session.c
> > index 778d82a..a252448 100644
> > --- a/src/spice-session.c
> > +++ b/src/spice-session.c
> > @@ -257,7 +257,7 @@ static void spice_session_init(SpiceSession *session)
> > g_free(channels);
> >
> > ring_init(&s->channels);
> > - s->images = cache_new((GDestroyNotify)pixman_image_unref);
> > + s->images = cache_image_new((GDestroyNotify)pixman_image_unref);
> > s->glz_window = glz_decoder_window_new();
> > update_proxy(session, NULL);
> > }
> > --
> > 1.9.5.msysgit.0
> >
> > _______________________________________________
> > Spice-devel mailing list
> > Spice-devel at lists.freedesktop.org
> > http://lists.freedesktop.org/mailman/listinfo/spice-devel
>
>
> Apart from the minors comments, that can or cannot be addressed (up to
> Sandy), the patch looks good to me.
> --
> Fabiano Fidêncio
>
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