Messages in this thread | | | Date | Mon, 24 Nov 2008 06:51:34 -0500 | From | Mathieu Desnoyers <> | Subject | Re: [ltt-dev] [RFC PATCH] Poll : add poll_wait_set_exclusive (fixing thundering herd problem in LTTng) |
| |
* KOSAKI Motohiro (kosaki.motohiro@jp.fujitsu.com) wrote: > Hi > > > static struct poll_table_entry *poll_get_entry(poll_table *_p) > > { > > struct poll_wqueues *p = container_of(_p, struct poll_wqueues, pt); > > @@ -117,8 +135,10 @@ static struct poll_table_entry *poll_get > > } > > > > /* Add a new entry */ > > -static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > > - poll_table *p) > > +static void __pollwait_common(struct file *filp, > > + wait_queue_head_t *wait_address, > > + poll_table *p, > > + int exclusive) > > { > > struct poll_table_entry *entry = poll_get_entry(p); > > if (!entry) > > @@ -127,7 +147,23 @@ static void __pollwait(struct file *filp > > entry->filp = filp; > > entry->wait_address = wait_address; > > init_waitqueue_entry(&entry->wait, current); > > - add_wait_queue(wait_address, &entry->wait); > > + if (!exclusive) > > + add_wait_queue(wait_address, &entry->wait); > > + else > > + add_wait_queue_exclusive(wait_address, &entry->wait); > > +} > > > I fully agreed this feature is needed. > Actually, I've made similar patch at one years ago. > > http://marc.info/?l=linux-kernel&m=120257050719087&w=2 > > > but, I have one question. > My version have epoll support, but yours donesn't have. > Is it intensionally? > > this is just dumb question, it doesn't mean any objection.
Hrm, actually, your patch seems cleaner than mine, but it adds a branch in the standard hotpath, which mine does not do (but I am not sure it is such an important optimization...). Is there any reason why your patch did not get merged ?
The only reason I did not make a epoll version is simply because LTTng currently does not support it. :)
Mathieu
-- Mathieu Desnoyers OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
| |