| lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
|
Open Source and information security mailing list archives
| ||
|
Message-ID: <4926F6C5.9030108@cosmosbay.com>
Date: Fri, 21 Nov 2008 18:58:29 +0100
From: Eric Dumazet <dada1@...mosbay.com>
To: Christoph Hellwig <hch@...radead.org>
CC: David Miller <davem@...emloft.net>, mingo@...e.hu,
cl@...ux-foundation.org, rjw@...k.pl, linux-kernel@...r.kernel.org,
kernel-testers@...r.kernel.org, efault@....de,
a.p.zijlstra@...llo.nl, Linux Netdev List <netdev@...r.kernel.org>,
viro@...iv.linux.org.uk, linux-fsdevel@...r.kernel.org
Subject: [PATCH] fs: pipe/sockets/anon dentries should have themselves as
parent
Christoph Hellwig a écrit :
> On Fri, Nov 21, 2008 at 04:13:38PM +0100, Eric Dumazet wrote:
>> [PATCH] fs: pipe/sockets/anon dentries should not have a parent
>>
>> Linking pipe/sockets/anon dentries to one root 'parent' has no functional
>> impact at all, but a scalability one.
>>
>> We can avoid touching a cache line at allocation stage (inside d_alloc(), no need
>> to touch root->d_count), but also at freeing time (in d_kill, decrementing d_count)
>> We avoid an expensive atomic_dec_and_lock() call on the root dentry.
>>
>> If we correct dnotify_parent() and inotify_d_instantiate() to take into account
>> a NULL d_parent, we can call d_alloc() with a NULL parent instead of root dentry.
>
> Sorry folks, but a NULL d_parent is a no-go from the VFS perspective,
> but you can set d_parent to the dentry itself which is the magic used
> for root of tree dentries. They should also be marked
> DCACHE_DISCONNECTED to make sure this is not unexpected.
>
> And this kind of stuff really needs to go through -fsdevel.
Thanks Christoph for your review, sorry for fsdevel being forgotten.
d_alloc_root() is not an option here, since we also want such dentries
to be unhashed. So here is a second version, with the introduction
of a new helper, d_alloc_unhashed(), to be used by pipes, sockets and anon
I got even better numbers, probably because dnotify/inotify dont have
the NULL d_parent test anymore.
[PATCH] fs: pipe/sockets/anon dentries should have themselves as parent
Linking pipe/sockets/anon dentries to one root 'parent' has no functional
impact at all, but a scalability one.
We can avoid touching a cache line at allocation stage (inside d_alloc(), no need
to touch root->d_count), but also at freeing time (in d_kill, decrementing d_count)
We avoid an expensive atomic_dec_and_lock() call on the root dentry.
We add d_alloc_unhashed(const char *name, struct inode *inode) helper
to be used by pipes/socket/anon. This function is about the same as
d_alloc_root() but for unhashed entries.
Before patch, time to run 8 * 1 million of close(socket()) calls on 8 CPUS was :
real 0m27.496s
user 0m0.657s
sys 3m39.092s
After patch :
real 0m23.843s
user 0m0.616s
sys 3m9.732s
Old oprofile :
CPU: Core 2, speed 3000.11 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples cum. samples % cum. % symbol name
164257 164257 11.0245 11.0245 init_file
155488 319745 10.4359 21.4604 d_alloc
151887 471632 10.1942 31.6547 _atomic_dec_and_lock
91620 563252 6.1493 37.8039 inet_create
74245 637497 4.9831 42.7871 kmem_cache_alloc
46702 684199 3.1345 45.9216 dentry_iput
46186 730385 3.0999 49.0215 tcp_close
42824 773209 2.8742 51.8957 kmem_cache_free
37275 810484 2.5018 54.3975 wake_up_inode
36553 847037 2.4533 56.8508 tcp_v4_init_sock
35661 882698 2.3935 59.2443 inotify_d_instantiate
32998 915696 2.2147 61.4590 sysenter_past_esp
31442 947138 2.1103 63.5693 d_instantiate
31303 978441 2.1010 65.6703 generic_forget_inode
27533 1005974 1.8479 67.5183 vfs_dq_drop
24237 1030211 1.6267 69.1450 sock_attach_fd
19290 1049501 1.2947 70.4397 __copy_from_user_ll
New oprofile :
CPU: Core 2, speed 3000.11 MHz (estimated)
Counted CPU_CLK_UNHALTED events (Clock cycles when not halted) with a unit mask of 0x00 (Unhalted core cycles) count 100000
samples cum. samples % cum. % symbol name
148703 148703 10.8581 10.8581 inet_create
116680 265383 8.5198 19.3779 new_inode
108912 374295 7.9526 27.3306 init_file
82911 457206 6.0541 33.3846 kmem_cache_alloc
65690 522896 4.7966 38.1812 wake_up_inode
53286 576182 3.8909 42.0721 _atomic_dec_and_lock
43814 619996 3.1992 45.2713 generic_forget_inode
41993 661989 3.0663 48.3376 d_alloc
41244 703233 3.0116 51.3492 kmem_cache_free
39244 742477 2.8655 54.2148 tcp_v4_init_sock
37402 779879 2.7310 56.9458 tcp_close
33336 813215 2.4342 59.3800 sysenter_past_esp
28596 841811 2.0880 61.4680 inode_has_buffers
25769 867580 1.8816 63.3496 d_kill
22606 890186 1.6507 65.0003 dentry_iput
20224 910410 1.4767 66.4770 vfs_dq_drop
19800 930210 1.4458 67.9228 __copy_from_user_ll
Signed-off-by: Eric Dumazet <dada1@...mosbay.com>
---
fs/anon_inodes.c | 9 +--------
fs/dcache.c | 31 +++++++++++++++++++++++++++++++
fs/pipe.c | 10 +---------
include/linux/dcache.h | 1 +
net/socket.c | 10 +---------
5 files changed, 35 insertions(+), 26 deletions(-)
View attachment "d_alloc_unhashed.patch" of type "text/plain" (4729 bytes)
Powered by blists - more mailing lists