From patchwork Tue Apr 28 15:06:11 2009 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Eric Dumazet X-Patchwork-Id: 26572 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@bilbo.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from ozlabs.org (ozlabs.org [203.10.76.45]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client CN "mx.ozlabs.org", Issuer "CA Cert Signing Authority" (verified OK)) by bilbo.ozlabs.org (Postfix) with ESMTPS id CAC53B7067 for ; Wed, 29 Apr 2009 01:07:43 +1000 (EST) Received: by ozlabs.org (Postfix) id BB3D4DDF0F; Wed, 29 Apr 2009 01:07:43 +1000 (EST) Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.176.167]) by ozlabs.org (Postfix) with ESMTP id 436EEDDF02 for ; Wed, 29 Apr 2009 01:07:43 +1000 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761761AbZD1PHZ (ORCPT ); Tue, 28 Apr 2009 11:07:25 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1761753AbZD1PHX (ORCPT ); Tue, 28 Apr 2009 11:07:23 -0400 Received: from gw1.cosmosbay.com ([212.99.114.194]:35484 "EHLO gw1.cosmosbay.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761728AbZD1PHV (ORCPT ); Tue, 28 Apr 2009 11:07:21 -0400 Received: from [127.0.0.1] (localhost [127.0.0.1]) by gw1.cosmosbay.com (8.13.7/8.13.7) with ESMTP id n3SF6BQA011721; Tue, 28 Apr 2009 17:06:11 +0200 Message-ID: <49F71B63.8010503@cosmosbay.com> Date: Tue, 28 Apr 2009 17:06:11 +0200 From: Eric Dumazet User-Agent: Thunderbird 2.0.0.21 (Windows/20090302) MIME-Version: 1.0 To: linux kernel CC: Andi Kleen , David Miller , cl@linux.com, jesse.brandeburg@intel.com, netdev@vger.kernel.org, haoki@redhat.com, mchan@broadcom.com, davidel@xmailserver.org, Ingo Molnar Subject: [PATCH] poll: Avoid extra wakeups in select/poll References: <49F3308B.1030507@cosmosbay.com> <20090426.020411.157511269.davem@davemloft.net> <49F43B8F.2050907@cosmosbay.com> <87ab60rh8t.fsf@basil.nowhere.org> In-Reply-To: <87ab60rh8t.fsf@basil.nowhere.org> X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-1.6 (gw1.cosmosbay.com [0.0.0.0]); Tue, 28 Apr 2009 17:06:12 +0200 (CEST) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org [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 Acked-by: David S. Miller Acked-by: Andi Kleen --- fs/select.c | 28 +++++++++++++++++++++++++--- include/linux/poll.h | 3 +++ 2 files changed, 28 insertions(+), 3 deletions(-) -- 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..2708187 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); @@ -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; @@ -685,8 +704,11 @@ 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; };