diff options
| author | Takashi Iwai <tiwai@suse.de> | 2022-06-10 08:45:37 +0200 |
|---|---|---|
| committer | Takashi Iwai <tiwai@suse.de> | 2022-06-15 07:44:55 +0200 |
| commit | c27e1efb61c545f36c450ef60862df9251d239a4 (patch) | |
| tree | 6f2fb08c61976cc820269fb10baa46ac8577d4ce /include/sound/core.h | |
| parent | b13baccc3850ca8b8cccbf8ed9912dbaa0fdf7f3 (diff) | |
| download | linux-c27e1efb61c545f36c450ef60862df9251d239a4.tar.bz2 | |
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>
Diffstat (limited to 'include/sound/core.h')
| -rw-r--r-- | include/sound/core.h | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/include/sound/core.h b/include/sound/core.h index 6d4cc49584c6..dd28de2343b8 100644 --- a/include/sound/core.h +++ b/include/sound/core.h @@ -14,6 +14,7 @@ #include <linux/pm.h> /* pm_message_t */ #include <linux/stringify.h> #include <linux/printk.h> +#include <linux/xarray.h> /* number of supported soundcards */ #ifdef CONFIG_SND_DYNAMIC_MINORS @@ -103,6 +104,11 @@ struct snd_card { size_t user_ctl_alloc_size; // current memory allocation by user controls. struct list_head controls; /* all controls for this card */ struct list_head ctl_files; /* active control files */ +#ifdef CONFIG_SND_CTL_FAST_LOOKUP + struct xarray ctl_numids; /* hash table for numids */ + struct xarray ctl_hash; /* hash table for ctl id matching */ + bool ctl_hash_collision; /* ctl_hash collision seen? */ +#endif struct snd_info_entry *proc_root; /* root for soundcard specific files */ struct proc_dir_entry *proc_root_link; /* number link to real id */ |