ALSA: control: Use xarray for faster lookups
The control elements are managed in a single linked list and we
traverse the whole list for matching each numid or ctl id per every
inquiry of a control element. This is OK-ish for a small number of
elements but obviously it doesn't scale. Especially the matching with
the ctl id takes time because it checks each field of the snd_ctl_id
element, e.g. the name string is matched with strcmp().
This patch adds the hash tables with Xarray for improving the lookup
speed of a control element. There are two xarray tables added to the
card; one for numid and another for ctl id. For the numid, we use the
numid as the index, while for the ctl id, we calculate a hash key.
The lookup is done via a single xa_load() execution. As long as the
given control element is found on the Xarray table, that's fine, we
can give back a quick lookup result. The problem is when no entry
hits on the table, and for this case, we have a slight optimization.
Namely, the driver checks whether we had a collision on Xarray table,
and do a fallback search (linear lookup of the full entries) only if a
hash key collision happened beforehand.
So, in theory, the inquiry for a non-existing element might take still
time even with this patch in a worst case, but this must be pretty
rare.
The feature is enabled via CONFIG_SND_CTL_FAST_LOOKUP, which is turned
on as default. For simplicity, the option can be turned off only when
CONFIG_EXPERT is set ("You are expert? Then you manage 1000 knobs").
Link: https://lore.kernel.org/r/20211028130027.18764-1-tiwai@suse.de
Link: https://lore.kernel.org/r/20220609180504.775-1-tiwai@suse.de
Link: https://lore.kernel.org/all/cover.1653813866.git.quic_rbankapu@quicinc.com/
Link: https://lore.kernel.org/r/20220610064537.18660-1-tiwai@suse.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
This commit is contained in:
Takashi Iwai
Родитель
b13baccc38
Коммит
c27e1efb61
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@ -14,6 +14,7 @@
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#include <linux/pm.h> /* pm_message_t */
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#include <linux/stringify.h>
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#include <linux/printk.h>
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#include <linux/xarray.h>
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/* number of supported soundcards */
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#ifdef CONFIG_SND_DYNAMIC_MINORS
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@ -103,6 +104,11 @@ struct snd_card {
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size_t user_ctl_alloc_size; // current memory allocation by user controls.
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struct list_head controls; /* all controls for this card */
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struct list_head ctl_files; /* active control files */
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#ifdef CONFIG_SND_CTL_FAST_LOOKUP
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struct xarray ctl_numids; /* hash table for numids */
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struct xarray ctl_hash; /* hash table for ctl id matching */
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bool ctl_hash_collision; /* ctl_hash collision seen? */
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#endif
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struct snd_info_entry *proc_root; /* root for soundcard specific files */
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struct proc_dir_entry *proc_root_link; /* number link to real id */
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@ -154,6 +154,16 @@ config SND_VERBOSE_PRINTK
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You don't need this unless you're debugging ALSA.
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config SND_CTL_FAST_LOOKUP
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bool "Fast lookup of control elements" if EXPERT
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default y
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select XARRAY_MULTI
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help
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This option enables the faster lookup of control elements.
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It will consume more memory because of the additional Xarray.
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If you want to choose the memory footprint over the performance
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inevitably, turn this off.
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config SND_DEBUG
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bool "Debug"
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help
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@ -364,6 +364,93 @@ static int snd_ctl_find_hole(struct snd_card *card, unsigned int count)
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return 0;
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}
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/* check whether the given id is contained in the given kctl */
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static bool elem_id_matches(const struct snd_kcontrol *kctl,
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const struct snd_ctl_elem_id *id)
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{
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return kctl->id.iface == id->iface &&
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kctl->id.device == id->device &&
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kctl->id.subdevice == id->subdevice &&
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!strncmp(kctl->id.name, id->name, sizeof(kctl->id.name)) &&
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kctl->id.index <= id->index &&
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kctl->id.index + kctl->count > id->index;
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}
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#ifdef CONFIG_SND_CTL_FAST_LOOKUP
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/* Compute a hash key for the corresponding ctl id
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* It's for the name lookup, hence the numid is excluded.
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* The hash key is bound in LONG_MAX to be used for Xarray key.
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*/
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#define MULTIPLIER 37
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static unsigned long get_ctl_id_hash(const struct snd_ctl_elem_id *id)
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{
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unsigned long h;
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const unsigned char *p;
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h = id->iface;
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h = MULTIPLIER * h + id->device;
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h = MULTIPLIER * h + id->subdevice;
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for (p = id->name; *p; p++)
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h = MULTIPLIER * h + *p;
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h = MULTIPLIER * h + id->index;
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h &= LONG_MAX;
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return h;
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}
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/* add hash entries to numid and ctl xarray tables */
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static void add_hash_entries(struct snd_card *card,
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struct snd_kcontrol *kcontrol)
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{
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struct snd_ctl_elem_id id = kcontrol->id;
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int i;
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xa_store_range(&card->ctl_numids, kcontrol->id.numid,
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kcontrol->id.numid + kcontrol->count - 1,
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kcontrol, GFP_KERNEL);
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for (i = 0; i < kcontrol->count; i++) {
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id.index = kcontrol->id.index + i;
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if (xa_insert(&card->ctl_hash, get_ctl_id_hash(&id),
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kcontrol, GFP_KERNEL)) {
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/* skip hash for this entry, noting we had collision */
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card->ctl_hash_collision = true;
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dev_dbg(card->dev, "ctl_hash collision %d:%s:%d\n",
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id.iface, id.name, id.index);
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}
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}
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}
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/* remove hash entries that have been added */
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static void remove_hash_entries(struct snd_card *card,
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struct snd_kcontrol *kcontrol)
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{
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struct snd_ctl_elem_id id = kcontrol->id;
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struct snd_kcontrol *matched;
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unsigned long h;
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int i;
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for (i = 0; i < kcontrol->count; i++) {
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xa_erase(&card->ctl_numids, id.numid);
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h = get_ctl_id_hash(&id);
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matched = xa_load(&card->ctl_hash, h);
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if (matched && (matched == kcontrol ||
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elem_id_matches(matched, &id)))
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xa_erase(&card->ctl_hash, h);
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id.index++;
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id.numid++;
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}
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}
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#else /* CONFIG_SND_CTL_FAST_LOOKUP */
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static inline void add_hash_entries(struct snd_card *card,
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struct snd_kcontrol *kcontrol)
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{
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}
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static inline void remove_hash_entries(struct snd_card *card,
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struct snd_kcontrol *kcontrol)
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{
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}
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#endif /* CONFIG_SND_CTL_FAST_LOOKUP */
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enum snd_ctl_add_mode {
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CTL_ADD_EXCLUSIVE, CTL_REPLACE, CTL_ADD_ON_REPLACE,
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};
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@ -408,6 +495,8 @@ static int __snd_ctl_add_replace(struct snd_card *card,
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kcontrol->id.numid = card->last_numid + 1;
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card->last_numid += kcontrol->count;
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add_hash_entries(card, kcontrol);
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for (idx = 0; idx < kcontrol->count; idx++)
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snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_ADD, kcontrol, idx);
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@ -479,6 +568,26 @@ int snd_ctl_replace(struct snd_card *card, struct snd_kcontrol *kcontrol,
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}
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EXPORT_SYMBOL(snd_ctl_replace);
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static int __snd_ctl_remove(struct snd_card *card,
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struct snd_kcontrol *kcontrol,
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bool remove_hash)
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{
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unsigned int idx;
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if (snd_BUG_ON(!card || !kcontrol))
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return -EINVAL;
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list_del(&kcontrol->list);
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if (remove_hash)
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remove_hash_entries(card, kcontrol);
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card->controls_count -= kcontrol->count;
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for (idx = 0; idx < kcontrol->count; idx++)
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snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_REMOVE, kcontrol, idx);
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snd_ctl_free_one(kcontrol);
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return 0;
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}
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/**
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* snd_ctl_remove - remove the control from the card and release it
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* @card: the card instance
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@ -492,16 +601,7 @@ EXPORT_SYMBOL(snd_ctl_replace);
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*/
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int snd_ctl_remove(struct snd_card *card, struct snd_kcontrol *kcontrol)
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{
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unsigned int idx;
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if (snd_BUG_ON(!card || !kcontrol))
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return -EINVAL;
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list_del(&kcontrol->list);
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card->controls_count -= kcontrol->count;
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for (idx = 0; idx < kcontrol->count; idx++)
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snd_ctl_notify_one(card, SNDRV_CTL_EVENT_MASK_REMOVE, kcontrol, idx);
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snd_ctl_free_one(kcontrol);
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return 0;
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return __snd_ctl_remove(card, kcontrol, true);
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}
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EXPORT_SYMBOL(snd_ctl_remove);
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@ -642,14 +742,30 @@ int snd_ctl_rename_id(struct snd_card *card, struct snd_ctl_elem_id *src_id,
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up_write(&card->controls_rwsem);
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return -ENOENT;
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}
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remove_hash_entries(card, kctl);
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kctl->id = *dst_id;
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kctl->id.numid = card->last_numid + 1;
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card->last_numid += kctl->count;
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add_hash_entries(card, kctl);
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up_write(&card->controls_rwsem);
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return 0;
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}
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EXPORT_SYMBOL(snd_ctl_rename_id);
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#ifndef CONFIG_SND_CTL_FAST_LOOKUP
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static struct snd_kcontrol *
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snd_ctl_find_numid_slow(struct snd_card *card, unsigned int numid)
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{
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struct snd_kcontrol *kctl;
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list_for_each_entry(kctl, &card->controls, list) {
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if (kctl->id.numid <= numid && kctl->id.numid + kctl->count > numid)
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return kctl;
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}
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return NULL;
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}
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#endif /* !CONFIG_SND_CTL_FAST_LOOKUP */
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/**
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* snd_ctl_find_numid - find the control instance with the given number-id
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* @card: the card instance
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@ -665,15 +781,13 @@ EXPORT_SYMBOL(snd_ctl_rename_id);
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*/
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struct snd_kcontrol *snd_ctl_find_numid(struct snd_card *card, unsigned int numid)
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{
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struct snd_kcontrol *kctl;
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if (snd_BUG_ON(!card || !numid))
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return NULL;
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list_for_each_entry(kctl, &card->controls, list) {
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if (kctl->id.numid <= numid && kctl->id.numid + kctl->count > numid)
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return kctl;
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}
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return NULL;
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#ifdef CONFIG_SND_CTL_FAST_LOOKUP
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return xa_load(&card->ctl_numids, numid);
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#else
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return snd_ctl_find_numid_slow(card, numid);
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#endif
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}
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EXPORT_SYMBOL(snd_ctl_find_numid);
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@ -699,21 +813,18 @@ struct snd_kcontrol *snd_ctl_find_id(struct snd_card *card,
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return NULL;
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if (id->numid != 0)
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return snd_ctl_find_numid(card, id->numid);
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list_for_each_entry(kctl, &card->controls, list) {
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if (kctl->id.iface != id->iface)
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continue;
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if (kctl->id.device != id->device)
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continue;
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if (kctl->id.subdevice != id->subdevice)
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continue;
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if (strncmp(kctl->id.name, id->name, sizeof(kctl->id.name)))
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continue;
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if (kctl->id.index > id->index)
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continue;
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if (kctl->id.index + kctl->count <= id->index)
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continue;
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#ifdef CONFIG_SND_CTL_FAST_LOOKUP
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kctl = xa_load(&card->ctl_hash, get_ctl_id_hash(id));
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if (kctl && elem_id_matches(kctl, id))
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return kctl;
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}
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if (!card->ctl_hash_collision)
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return NULL; /* we can rely on only hash table */
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#endif
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/* no matching in hash table - try all as the last resort */
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list_for_each_entry(kctl, &card->controls, list)
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if (elem_id_matches(kctl, id))
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return kctl;
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return NULL;
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}
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EXPORT_SYMBOL(snd_ctl_find_id);
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@ -2195,8 +2306,13 @@ static int snd_ctl_dev_free(struct snd_device *device)
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down_write(&card->controls_rwsem);
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while (!list_empty(&card->controls)) {
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control = snd_kcontrol(card->controls.next);
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snd_ctl_remove(card, control);
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__snd_ctl_remove(card, control, false);
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}
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#ifdef CONFIG_SND_CTL_FAST_LOOKUP
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xa_destroy(&card->ctl_numids);
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xa_destroy(&card->ctl_hash);
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#endif
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up_write(&card->controls_rwsem);
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put_device(&card->ctl_dev);
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return 0;
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@ -310,6 +310,10 @@ static int snd_card_init(struct snd_card *card, struct device *parent,
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rwlock_init(&card->ctl_files_rwlock);
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INIT_LIST_HEAD(&card->controls);
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INIT_LIST_HEAD(&card->ctl_files);
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#ifdef CONFIG_SND_CTL_FAST_LOOKUP
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xa_init(&card->ctl_numids);
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xa_init(&card->ctl_hash);
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#endif
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spin_lock_init(&card->files_lock);
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INIT_LIST_HEAD(&card->files_list);
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mutex_init(&card->memory_mutex);
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