From: Eric Dumazet <dada1-fPLkHRcR87vqlBn2x/YWAg@public•gmane.org>
To: Ingo Molnar <mingo-X9Un+BFzKDI@public•gmane.org>
Cc: Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public•gmane.org>,
David Miller <davem-fT/PcQaiUtIeIZ0/mPfg9Q@public•gmane.org>,
"Rafael J. Wysocki" <rjw-KKrjLPT3xs0@public•gmane.org>,
linux-kernel-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
kernel-testers-u79uwXL29TY76Z2rM5mHXA@public•gmane.org,
Mike Galbraith <efault-Mmb7MZpHnFY@public•gmane.org>,
Peter Zijlstra
<a.p.zijlstra-/NLkJaSkS4VmR6Xm/wNWPw@public•gmane.org>,
Linux Netdev List
<netdev-u79uwXL29TY76Z2rM5mHXA@public•gmane.org>,
Christoph Lameter
<cl-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public•gmane.org>,
Christoph Hellwig <hch-wEGCiKHe2LqWVfeAwA7xHQ@public•gmane.org>,
rth-hL46jP5Bxq7R7s880joybQ@public•gmane.org,
ink-biIs/Y0ymYJMZLIVYojuPNP0rXTJTi09@public•gmane.org
Subject: Re: [PATCH 6/6] fs: Introduce kern_mount_special() to mount special vfs
Date: Fri, 28 Nov 2008 23:20:24 +0100 [thread overview]
Message-ID: <49306EA8.1050801@cosmosbay.com> (raw)
In-Reply-To: <20081128180220.GK10487-X9Un+BFzKDI@public.gmane.org>
Ingo Molnar a écrit :
> * Al Viro <viro-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public•gmane.org> wrote:
>
>> On Thu, Nov 27, 2008 at 12:32:59AM +0100, Eric Dumazet wrote:
>>> This function arms a flag (MNT_SPECIAL) on the vfs, to avoid
>>> refcounting on permanent system vfs.
>>> Use this function for sockets, pipes, anonymous fds.
>> IMO that's pushing it past the point of usefulness; unless you can show
>> that this really gives considerable win on pipes et.al. *AND* that it
>> doesn't hurt other loads...
>
> The numbers look pretty convincing:
>
>>> (socket8 bench result : from 2.94s to 2.23s)
>
> And i wouldnt expect it to hurt real-filesystem workloads.
>
> Here's the contemporary trace of a typical ext3- sys_open():
>
> 0) | sys_open() {
> 0) | do_sys_open() {
> 0) | getname() {
> 0) 0.367 us | kmem_cache_alloc();
> 0) | strncpy_from_user(); {
> 0) | _cond_resched() {
> 0) | need_resched() {
> 0) 0.363 us | constant_test_bit();
> 0) 1. 47 us | }
> 0) 1.815 us | }
> 0) 2.587 us | }
> 0) 4. 22 us | }
> 0) | alloc_fd() {
> 0) 0.480 us | _spin_lock();
> 0) 0.487 us | expand_files();
> 0) 2.356 us | }
> 0) | do_filp_open() {
> 0) | path_lookup_open() {
> 0) | get_empty_filp() {
> 0) 0.439 us | kmem_cache_alloc();
> 0) | security_file_alloc() {
> 0) 0.316 us | cap_file_alloc_security();
> 0) 1. 87 us | }
> 0) 3.189 us | }
> 0) | do_path_lookup() {
> 0) 0.366 us | _read_lock();
> 0) | path_walk() {
> 0) | __link_path_walk() {
> 0) | inode_permission() {
> 0) | ext3_permission() {
> 0) 0.441 us | generic_permission();
> 0) 1.247 us | }
> 0) | security_inode_permission() {
> 0) 0.411 us | cap_inode_permission();
> 0) 1.186 us | }
> 0) 3.555 us | }
> 0) | do_lookup() {
> 0) | __d_lookup() {
> 0) 0.486 us | _spin_lock();
> 0) 1.369 us | }
> 0) 0.442 us | __follow_mount();
> 0) 3. 14 us | }
> 0) | path_to_nameidata() {
> 0) 0.476 us | dput();
> 0) 1.235 us | }
> 0) | inode_permission() {
> 0) | ext3_permission() {
> 0) | generic_permission() {
> 0) | in_group_p() {
> 0) 0.410 us | groups_search();
> 0) 1.172 us | }
> 0) 1.994 us | }
> 0) 2.789 us | }
> 0) | security_inode_permission() {
> 0) 0.454 us | cap_inode_permission();
> 0) 1.238 us | }
> 0) 5.262 us | }
> 0) | do_lookup() {
> 0) | __d_lookup() {
> 0) 0.480 us | _spin_lock();
> 0) 1.621 us | }
> 0) 0.456 us | __follow_mount();
> 0) 3.215 us | }
> 0) | path_to_nameidata() {
> 0) 0.420 us | dput();
> 0) 1.193 us | }
> 0) + 23.551 us | }
> 0) | path_put() {
> 0) 0.420 us | dput();
> 0) | mntput() {
> 0) 0.359 us | mntput_no_expire();
> 0) 1. 50 us | }
> 0) 2.544 us | }
> 0) + 27.253 us | }
> 0) + 28.850 us | }
> 0) + 33.217 us | }
> 0) | may_open() {
> 0) | inode_permission() {
> 0) | ext3_permission() {
> 0) 0.480 us | generic_permission();
> 0) 1.229 us | }
> 0) | security_inode_permission() {
> 0) 0.405 us | cap_inode_permission();
> 0) 1.196 us | }
> 0) 3.589 us | }
> 0) 4.600 us | }
> 0) | nameidata_to_filp() {
> 0) | __dentry_open() {
> 0) | file_move() {
> 0) 0.470 us | _spin_lock();
> 0) 1.243 us | }
> 0) | security_dentry_open() {
> 0) 0.344 us | cap_dentry_open();
> 0) 1.139 us | }
> 0) 0.412 us | generic_file_open();
> 0) 0.561 us | file_ra_state_init();
> 0) 5.714 us | }
> 0) 6.483 us | }
> 0) + 46.494 us | }
> 0) 0.453 us | inotify_dentry_parent_queue_event();
> 0) 0.403 us | inotify_inode_queue_event();
> 0) | fd_install() {
> 0) 0.440 us | _spin_lock();
> 0) 1.247 us | }
> 0) | putname() {
> 0) | kmem_cache_free() {
> 0) | virt_to_head_page() {
> 0) 0.369 us | constant_test_bit();
> 0) 1. 23 us | }
> 0) 1.738 us | }
> 0) 2.422 us | }
> 0) + 60.560 us | }
> 0) + 61.368 us | }
>
> and here's a sys_close():
>
> 0) | sys_close() {
> 0) 0.540 us | _spin_lock();
> 0) | filp_close() {
> 0) 0.437 us | dnotify_flush();
> 0) 0.401 us | locks_remove_posix();
> 0) 0.349 us | fput();
> 0) 2.679 us | }
> 0) 4.452 us | }
>
> i'd be surprised to see a flag to show up in that codepath. Eric, does
> your testing confirm that?
On a socket/pipe, definitly no, because inode->i_sb->s_flags is not contended.
But on a shared inode, it might hurt :
offsetof(struct inode, i_count)=0x24
offsetof(struct inode, i_lock)=0x70
offsetof(struct inode, i_sb)=0x9c
offsetof(struct inode, i_writecount)=0x144
So i_sb sits in a probably contended cache line
I wonder why i_writecount sits so far from i_count, that doesnt make sense.
next prev parent reply other threads:[~2008-11-28 22:20 UTC|newest]
Thread overview: 75+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <Pine.LNX.4.64.0811201727070.9089@quilx.com>
[not found] ` <20081121083044.GL16242@elte.hu>
[not found] ` <49267694.1030506@cosmosbay.com>
[not found] ` <20081121.010508.40225532.davem@davemloft.net>
[not found] ` <4926AEDB.10007@cosmosbay.com>
[not found] ` <4926AEDB.10007-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-21 15:13 ` [PATCH] fs: pipe/sockets/anon dentries should not have a parent Eric Dumazet
[not found] ` <4926D022.5060008-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-21 15:21 ` Ingo Molnar
[not found] ` <20081121152148.GA20388-X9Un+BFzKDI@public.gmane.org>
2008-11-21 15:28 ` Eric Dumazet
[not found] ` <4926D39D.9050603-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-21 15:34 ` Ingo Molnar
2008-11-26 23:27 ` [PATCH 0/6] fs: Scalability of sockets/pipes allocation/deallocation on SMP Eric Dumazet
2008-11-27 9:39 ` Christoph Hellwig
2008-11-28 18:03 ` Ingo Molnar
[not found] ` <20081128180318.GL10487-X9Un+BFzKDI@public.gmane.org>
2008-11-28 18:47 ` Peter Zijlstra
2008-11-29 6:38 ` Christoph Hellwig
[not found] ` <20081129063816.GA869-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2008-11-29 8:07 ` Eric Dumazet
2008-11-29 8:43 ` [PATCH v2 0/5] " Eric Dumazet
2008-12-11 22:38 ` [PATCH v3 0/7] " Eric Dumazet
2008-12-11 22:38 ` [PATCH v3 1/7] fs: Use a percpu_counter to track nr_dentry Eric Dumazet
2007-07-24 1:24 ` Nick Piggin
[not found] ` <49419680.8010409-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-12-16 21:04 ` Paul E. McKenney
2008-12-11 22:39 ` [PATCH v3 2/7] fs: Use a percpu_counter to track nr_inodes Eric Dumazet
[not found] ` <4941968E.3020201-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2007-07-24 1:30 ` Nick Piggin
[not found] ` <200707241130.56767.nickpiggin-/E1597aS9LT0CCvOHzKKcA@public.gmane.org>
2008-12-12 5:11 ` Eric Dumazet
2008-12-16 21:10 ` Paul E. McKenney
2008-12-11 22:39 ` [PATCH v3 3/7] fs: Introduce a per_cpu last_ino allocator Eric Dumazet
2007-07-24 1:34 ` Nick Piggin
2008-12-16 21:26 ` Paul E. McKenney
2008-12-11 22:39 ` [PATCH v3 4/7] fs: Introduce SINGLE dentries for pipes, socket, anon fd Eric Dumazet
[not found] ` <494196AA.6080002-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-12-16 21:40 ` Paul E. McKenney
2008-12-11 22:40 ` [PATCH v3 5/7] fs: new_inode_single() and iput_single() Eric Dumazet
2008-12-16 21:41 ` Paul E. McKenney
[not found] ` <493100B0.6090104-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-12-11 22:40 ` [PATCH v3 6/7] fs: struct file move from call_rcu() to SLAB_DESTROY_BY_RCU Eric Dumazet
2007-07-24 1:13 ` Nick Piggin
2008-12-12 2:50 ` Nick Piggin
2008-12-12 4:45 ` Eric Dumazet
[not found] ` <4941EC65.5040903-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-12-12 16:48 ` Eric Dumazet
[not found] ` <494295C6.2020906-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-12-13 2:07 ` Christoph Lameter
[not found] ` <Pine.LNX.4.64.0812121958470.15781-dRBSpnHQED8AvxtiuMwx3w@public.gmane.org>
2008-12-17 20:25 ` Eric Dumazet
2008-12-13 1:41 ` Christoph Lameter
2008-12-11 22:41 ` [PATCH v3 7/7] fs: MS_NOREFCOUNT Eric Dumazet
[not found] ` <492DDB6A.8090806-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 1:37 ` [PATCH 0/6] fs: Scalability of sockets/pipes allocation/deallocation on SMP Christoph Lameter
[not found] ` <Pine.LNX.4.64.0811261935330.31159-dRBSpnHQED8AvxtiuMwx3w@public.gmane.org>
2008-11-27 6:27 ` Eric Dumazet
[not found] ` <492E3DEF.8030602-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 14:44 ` Christoph Lameter
2008-11-29 8:43 ` [PATCH v2 1/5] fs: Use a percpu_counter to track nr_dentry Eric Dumazet
2008-11-29 8:43 ` [PATCH v2 2/5] fs: Use a percpu_counter to track nr_inodes Eric Dumazet
2008-11-29 8:44 ` [PATCH v2 4/5] fs: Introduce SINGLE dentries for pipes, socket, anon fd Eric Dumazet
[not found] ` <493100E7.3030907-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-29 10:38 ` Jörn Engel
[not found] ` <20081129103836.GA11959-PCqxUs/MD9bYtjvyW6yDsg@public.gmane.org>
2008-11-29 11:14 ` Eric Dumazet
2008-11-29 8:45 ` [PATCH v2 5/5] fs: new_inode_single() and iput_single() Eric Dumazet
2008-11-29 11:14 ` Jörn Engel
2008-11-29 8:44 ` [PATCH v2 3/5] fs: Introduce a per_cpu last_ino allocator Eric Dumazet
2008-11-26 23:32 ` [PATCH 3/6] " Eric Dumazet
[not found] ` <492DDC88.2050305-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 9:46 ` Christoph Hellwig
[not found] ` <20081121153453.GA23713-X9Un+BFzKDI@public.gmane.org>
2008-11-26 23:30 ` [PATCH 1/6] fs: Introduce a per_cpu nr_dentry Eric Dumazet
[not found] ` <492DDC0B.8060804-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 9:41 ` Christoph Hellwig
2008-11-26 23:32 ` [PATCH 4/6] fs: Introduce a per_cpu nr_inodes Eric Dumazet
2008-11-27 9:32 ` Peter Zijlstra
2008-11-27 9:39 ` Peter Zijlstra
2008-11-27 9:48 ` Christoph Hellwig
2008-11-27 10:01 ` Eric Dumazet
2008-11-27 10:07 ` Andi Kleen
2008-11-27 14:46 ` Christoph Lameter
2008-11-26 23:32 ` [PATCH 5/6] fs: Introduce special inodes Eric Dumazet
[not found] ` <492DDC99.5060106-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 8:20 ` David Miller
2008-11-26 23:32 ` [PATCH 6/6] fs: Introduce kern_mount_special() to mount special vfs Eric Dumazet
2008-11-27 9:53 ` Christoph Hellwig
[not found] ` <20081127095321.GE13860-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org>
2008-11-27 10:04 ` Eric Dumazet
[not found] ` <492E70B6.70108-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 10:10 ` Christoph Hellwig
[not found] ` <492DDCAB.1070204-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-27 8:21 ` David Miller
2008-11-28 9:26 ` Al Viro
[not found] ` <20081128092604.GL28946-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2008-11-28 9:34 ` Al Viro
2008-11-28 18:02 ` Ingo Molnar
2008-11-28 18:58 ` Ingo Molnar
[not found] ` <20081128180220.GK10487-X9Un+BFzKDI@public.gmane.org>
2008-11-28 22:20 ` Eric Dumazet [this message]
2008-11-28 22:37 ` Eric Dumazet
2008-11-28 22:43 ` Eric Dumazet
2008-11-21 15:36 ` [PATCH] fs: pipe/sockets/anon dentries should not have a parent Christoph Hellwig
2008-11-21 17:58 ` [PATCH] fs: pipe/sockets/anon dentries should have themselves as parent Eric Dumazet
[not found] ` <4926F6C5.9030108-fPLkHRcR87vqlBn2x/YWAg@public.gmane.org>
2008-11-21 18:43 ` Matthew Wilcox
2008-11-23 3:53 ` Eric Dumazet
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