On Thu, 03 Apr 2008 13:52:43 +0800
Li Zefan <[EMAIL PROTECTED]> wrote:
> +/* hash table for cgroup groups. This improves the performance to
> + * find an existing css_set */
> +#define CSS_SET_HASH_BITS 7
> +#define CSS_SET_TABLE_SIZE (1 << CSS_SET_HASH_BITS)
> +static struct hlist_head css_set_table[CSS_SET_TABLE_SIZE];
How above number is selected ?
> +static struct hlist_head *css_set_hash(struct cgroup_subsys_state *css[])
> +{
> + int i;
> + int index;
> + unsigned long tmp = 0UL;
> +
> + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
> + tmp += (unsigned long)css[i];
> +
maybe css[i]'s lower 2-3 bits will be ignored. because thery are always 0.
And I don't like "+" for hash. how about
==
for (i = 0; i < CGROUP_SUBSYS_COUNT; i++)
unsigned long x;
x = (unsigned long)css[i];
tmp = (x >> 16) ^ (x & 0xffff)
==
or some func, which uses full bits.
> + index = hash_long(tmp, CSS_SET_HASH_BITS);
> +
> + return &css_set_table[index];
> +}
> +
> /* We don't maintain the lists running through each css_set to its
> * task until after the first call to cgroup_iter_start(). This
> * reduces the fork()/exit() overhead for people who have cgroups
> @@ -219,6 +240,7 @@ static int use_task_css_set_links;
> static void unlink_css_set(struct css_set *cg)
> {
> write_lock(&css_set_lock);
> + hlist_del(&cg->hlist);
> list_del(&cg->list);
> css_set_count--;
This css_set_lock is worth to be rwlock ?
how about per hashline spinlock ? (but per-hashline seems overkill..)
Thanks,
-Kame
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