| Message ID | 49F81FB9.50504@cosmosbay.com |
|---|---|
| State | Not Applicable, archived |
| Delegated to: | David Miller |
| Headers | show |
* Eric Dumazet <dada1@cosmosbay.com> wrote: > Ingo Molnar a écrit : > > * Eric Dumazet <dada1@cosmosbay.com> wrote: > > > >> @@ -418,8 +429,16 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time) > >> if (file) { > >> f_op = file->f_op; > >> mask = DEFAULT_POLLMASK; > >> - if (f_op && f_op->poll) > >> + if (f_op && f_op->poll) { > >> + if (wait) { > >> + wait->key = POLLEX_SET; > >> + if (in & bit) > >> + wait->key |= POLLIN_SET; > >> + if (out & bit) > >> + wait->key |= POLLOUT_SET; > >> + } > >> mask = (*f_op->poll)(file, retval ? NULL : wait); > >> + } > >> fput_light(file, fput_needed); > >> if ((mask & POLLIN_SET) && (in & bit)) { > >> res_in |= bit; > > > > Please factor this whole 'if (file)' branch out into a helper. > > Typical indentation levels go from 1 to 3 tabs - 4 should be avoided > > if possible and 5 is pretty excessive already. This goes to eight. > > > > Thanks Ingo, > > Here is v3 of patch, with your Acked-by included :) > > This is IMHO clearer since helper immediatly follows POLLIN_SET / POLLOUT_SET / > POLLEX_SET defines. > > [PATCH] poll: Avoid extra wakeups in select/poll > > After introduction of keyed wakeups Davide Libenzi did on epoll, we > are able to avoid spurious wakeups in poll()/select() code too. > > For example, typical use of poll()/select() is to wait for incoming > network frames on many sockets. But TX completion for UDP/TCP > frames call sock_wfree() which in turn schedules thread. > > When scheduled, thread does a full scan of all polled fds and > can sleep again, because nothing is really available. If number > of fds is large, this cause significant load. > > This patch makes select()/poll() aware of keyed wakeups and > useless wakeups are avoided. This reduces number of context > switches by about 50% on some setups, and work performed > by sofirq handlers. > > Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> > Acked-by: David S. Miller <davem@davemloft.net> > Acked-by: Andi Kleen <ak@linux.intel.com> > Acked-by: Ingo Molnar <mingo@elte.hu> > --- > fs/select.c | 40 ++++++++++++++++++++++++++++++++++++---- > include/linux/poll.h | 3 +++ > 2 files changed, 39 insertions(+), 4 deletions(-) > > diff --git a/fs/select.c b/fs/select.c > index 0fe0e14..ba068ad 100644 > --- a/fs/select.c > +++ b/fs/select.c > @@ -168,7 +168,7 @@ static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) > return table->entry++; > } > > -static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) > +static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) > { > struct poll_wqueues *pwq = wait->private; > DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); > @@ -194,6 +194,16 @@ static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) > return default_wake_function(&dummy_wait, mode, sync, key); > } > > +static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) > +{ > + struct poll_table_entry *entry; > + > + entry = container_of(wait, struct poll_table_entry, wait); > + if (key && !((unsigned long)key & entry->key)) > + return 0; > + return __pollwake(wait, mode, sync, key); > +} > + > /* Add a new entry */ > static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > poll_table *p) > @@ -205,6 +215,7 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, > get_file(filp); > entry->filp = filp; > entry->wait_address = wait_address; > + entry->key = p->key; > init_waitqueue_func_entry(&entry->wait, pollwake); > entry->wait.private = pwq; > add_wait_queue(wait_address, &entry->wait); > @@ -362,6 +373,18 @@ get_max: > #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) > #define POLLEX_SET (POLLPRI) > > +static void wait_key_set(poll_table *wait, unsigned long in, > + unsigned long out, unsigned long bit) > +{ > + if (wait) { > + wait->key = POLLEX_SET; > + if (in & bit) > + wait->key |= POLLIN_SET; > + if (out & bit) > + wait->key |= POLLOUT_SET; > + } > +} should be inline perhaps? > + > int do_select(int n, fd_set_bits *fds, struct timespec *end_time) > { > ktime_t expire, *to = NULL; > @@ -418,20 +441,25 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time) > if (file) { > f_op = file->f_op; > mask = DEFAULT_POLLMASK; > - if (f_op && f_op->poll) > - mask = (*f_op->poll)(file, retval ? NULL : wait); > + if (f_op && f_op->poll) { > + wait_key_set(wait, in, out, bit); > + mask = (*f_op->poll)(file, wait); > + } > fput_light(file, fput_needed); > if ((mask & POLLIN_SET) && (in & bit)) { > res_in |= bit; > retval++; > + wait = NULL; > } > if ((mask & POLLOUT_SET) && (out & bit)) { > res_out |= bit; > retval++; > + wait = NULL; > } > if ((mask & POLLEX_SET) && (ex & bit)) { > res_ex |= bit; > retval++; > + wait = NULL; > } > } > } Looks much nicer now! [ I'd still suggest to factor out the guts of do_select() as its nesting is excessive that hurts its reviewability quite a bit - but now your patch does not make the situation any worse. ] Even-More-Acked-by: Ingo Molnar <mingo@elte.hu> Ingo -- 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/fs/select.c b/fs/select.c index 0fe0e14..ba068ad 100644 --- a/fs/select.c +++ b/fs/select.c @@ -168,7 +168,7 @@ static struct poll_table_entry *poll_get_entry(struct poll_wqueues *p) return table->entry++; } -static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) +static int __pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) { struct poll_wqueues *pwq = wait->private; DECLARE_WAITQUEUE(dummy_wait, pwq->polling_task); @@ -194,6 +194,16 @@ static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) return default_wake_function(&dummy_wait, mode, sync, key); } +static int pollwake(wait_queue_t *wait, unsigned mode, int sync, void *key) +{ + struct poll_table_entry *entry; + + entry = container_of(wait, struct poll_table_entry, wait); + if (key && !((unsigned long)key & entry->key)) + return 0; + return __pollwake(wait, mode, sync, key); +} + /* Add a new entry */ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, poll_table *p) @@ -205,6 +215,7 @@ static void __pollwait(struct file *filp, wait_queue_head_t *wait_address, get_file(filp); entry->filp = filp; entry->wait_address = wait_address; + entry->key = p->key; init_waitqueue_func_entry(&entry->wait, pollwake); entry->wait.private = pwq; add_wait_queue(wait_address, &entry->wait); @@ -362,6 +373,18 @@ get_max: #define POLLOUT_SET (POLLWRBAND | POLLWRNORM | POLLOUT | POLLERR) #define POLLEX_SET (POLLPRI) +static void wait_key_set(poll_table *wait, unsigned long in, + unsigned long out, unsigned long bit) +{ + if (wait) { + wait->key = POLLEX_SET; + if (in & bit) + wait->key |= POLLIN_SET; + if (out & bit) + wait->key |= POLLOUT_SET; + } +} + int do_select(int n, fd_set_bits *fds, struct timespec *end_time) { ktime_t expire, *to = NULL; @@ -418,20 +441,25 @@ int do_select(int n, fd_set_bits *fds, struct timespec *end_time) if (file) { f_op = file->f_op; mask = DEFAULT_POLLMASK; - if (f_op && f_op->poll) - mask = (*f_op->poll)(file, retval ? NULL : wait); + if (f_op && f_op->poll) { + wait_key_set(wait, in, out, bit); + mask = (*f_op->poll)(file, wait); + } fput_light(file, fput_needed); if ((mask & POLLIN_SET) && (in & bit)) { res_in |= bit; retval++; + wait = NULL; } if ((mask & POLLOUT_SET) && (out & bit)) { res_out |= bit; retval++; + wait = NULL; } if ((mask & POLLEX_SET) && (ex & bit)) { res_ex |= bit; retval++; + wait = NULL; } } } @@ -685,8 +713,12 @@ static inline unsigned int do_pollfd(struct pollfd *pollfd, poll_table *pwait) mask = POLLNVAL; if (file != NULL) { mask = DEFAULT_POLLMASK; - if (file->f_op && file->f_op->poll) + if (file->f_op && file->f_op->poll) { + if (pwait) + pwait->key = pollfd->events | + POLLERR | POLLHUP; mask = file->f_op->poll(file, pwait); + } /* Mask out unneeded events. */ mask &= pollfd->events | POLLERR | POLLHUP; fput_light(file, fput_needed); diff --git a/include/linux/poll.h b/include/linux/poll.h index 8c24ef8..3327389 100644 --- a/include/linux/poll.h +++ b/include/linux/poll.h @@ -32,6 +32,7 @@ typedef void (*poll_queue_proc)(struct file *, wait_queue_head_t *, struct poll_ typedef struct poll_table_struct { poll_queue_proc qproc; + unsigned long key; } poll_table; static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_address, poll_table *p) @@ -43,10 +44,12 @@ static inline void poll_wait(struct file * filp, wait_queue_head_t * wait_addres static inline void init_poll_funcptr(poll_table *pt, poll_queue_proc qproc) { pt->qproc = qproc; + pt->key = ~0UL; /* all events enabled */ } struct poll_table_entry { struct file *filp; + unsigned long key; wait_queue_t wait; wait_queue_head_t *wait_address; };