| Message ID | 20150319194608.GA27962@casper.infradead.org |
|---|---|
| State | Superseded, archived |
| Delegated to: | David Miller |
| Headers | show |
On Thu, Mar 19, 2015 at 07:46:08PM +0000, Thomas Graf wrote: > The current code correctly limits table size to the next power of two. > This check is solely to catch programming errors. > > Signed-off-by: Thomas Graf <tgraf@suug.ch> I don't see the point of this. A maximum size of 3 says that the table size should never exceed 3 which makes perfect sense. And our current code will respect that. So why force it to be a power of 2 just because our table sizes happen to be powers of 2? Cheers,
On 03/20/15 at 08:02am, Herbert Xu wrote: > On Thu, Mar 19, 2015 at 07:46:08PM +0000, Thomas Graf wrote: > > The current code correctly limits table size to the next power of two. > > This check is solely to catch programming errors. > > > > Signed-off-by: Thomas Graf <tgraf@suug.ch> > > I don't see the point of this. A maximum size of 3 says that > the table size should never exceed 3 which makes perfect sense. > And our current code will respect that. > > So why force it to be a power of 2 just because our table sizes > happen to be powers of 2? rht_grow_above_75() checks the old table size: (!ht->p.max_size || tbl->size < ht->p.max_size); If you specify max_size = 3, it grows the table to tbl->size = 4. This can be avoided if max_size is a power of two. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Thu, Mar 19, 2015 at 09:15:46PM +0000, Thomas Graf wrote: > > rht_grow_above_75() checks the old table size: > > (!ht->p.max_size || tbl->size < ht->p.max_size); > > If you specify max_size = 3, it grows the table to tbl->size = 4. > This can be avoided if max_size is a power of two. OK let's fix the test then. The easiest way would be to round max_size up to the next power of 2. Cheers,
On Fri, Mar 20, 2015 at 08:49:33AM +1100, Herbert Xu wrote: > > OK let's fix the test then. The easiest way would be to round > max_size up to the next power of 2. s/up/down/
From: Herbert Xu > Sent: 19 March 2015 21:50 > On Thu, Mar 19, 2015 at 09:15:46PM +0000, Thomas Graf wrote: > > > > rht_grow_above_75() checks the old table size: > > > > (!ht->p.max_size || tbl->size < ht->p.max_size); > > > > If you specify max_size = 3, it grows the table to tbl->size = 4. > > This can be avoided if max_size is a power of two. > > OK let's fix the test then. The easiest way would be to round > max_size up to the next power of 2. Isn't that round-up implicit in the test above, no reason to change the user-supplied limit. To round down just test tbl->size * 2 <= ht->p.max_size. Maybe just document the fact that it will grow if the current size is less than the requested maximum. David -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/lib/rhashtable.c b/lib/rhashtable.c index 5f8fe3e..5474507 100644 --- a/lib/rhashtable.c +++ b/lib/rhashtable.c @@ -933,6 +933,9 @@ int rhashtable_init(struct rhashtable *ht, struct rhashtable_params *params) if (params->nulls_base && params->nulls_base < (1U << RHT_BASE_SHIFT)) return -EINVAL; + WARN_ON(params->min_size && !is_power_of_2(params->min_size)); + WARN_ON(params->max_size && !is_power_of_2(params->max_size)); + params->min_size = max(params->min_size, HASH_MIN_SIZE); if (params->nelem_hint)
The current code correctly limits table size to the next power of two. This check is solely to catch programming errors. Signed-off-by: Thomas Graf <tgraf@suug.ch> --- v2: use is_power_of_2() instead of roundup_pow_of_two() lib/rhashtable.c | 3 +++ 1 file changed, 3 insertions(+)