From: Eric Dumazet <eric.dumazet@gmail.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: Alan Burlison <Alan.Burlison@oracle.com>,
Casper.Dik@oracle.com, David Miller <davem@davemloft.net>,
stephen@networkplumber.org, netdev@vger.kernel.org,
dholland-tech@netbsd.org
Subject: Re: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3)
Date: Tue, 27 Oct 2015 17:13:56 -0700 [thread overview]
Message-ID: <1445991236.7476.59.camel@edumazet-glaptop2.roam.corp.google.com> (raw)
In-Reply-To: <20151027231702.GA22011@ZenIV.linux.org.uk>
On Tue, 2015-10-27 at 23:17 +0000, Al Viro wrote:
> * [Linux-specific aside] our __alloc_fd() can degrade quite badly
> with some use patterns. The cacheline pingpong in the bitmap is probably
> inevitable, unless we accept considerably heavier memory footprint,
> but we also have a case when alloc_fd() takes O(n) and it's _not_ hard
> to trigger - close(3);open(...); will have the next open() after that
> scanning the entire in-use bitmap. I think I see a way to improve it
> without slowing the normal case down, but I'll need to experiment a
> bit before I post patches. Anybody with examples of real-world loads
> that make our descriptor allocator to degrade is very welcome to post
> the reproducers...
Well, I do have real-world loads, but quite hard to setup in a lab :(
Note that we also hit the 'struct cred'->usage refcount for every
open()/close()/sock_alloc(), and simply moving uid/gid out of the first
cache line really helps, as current_fsuid() and current_fsgid() no
longer forces a pingpong.
I moved seldom used fields on the first cache line, so that overall
memory usage did not change (192 bytes on 64 bit arches)
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 8d70e1361ecd..460efae83522 100644
--- a/include/linux/cred.h
+++ b/include/linux/cred.h
@@ -124,7 +124,17 @@ struct cred {
#define CRED_MAGIC 0x43736564
#define CRED_MAGIC_DEAD 0x44656144
#endif
- kuid_t uid; /* real UID of the task */
+ struct rcu_head rcu; /* RCU deletion hook */
+
+ kernel_cap_t cap_inheritable; /* caps our children can inherit */
+ kernel_cap_t cap_permitted; /* caps we're permitted */
+ kernel_cap_t cap_effective; /* caps we can actually use */
+ kernel_cap_t cap_bset; /* capability bounding set */
+ kernel_cap_t cap_ambient; /* Ambient capability set */
+
+ kuid_t uid ____cacheline_aligned_in_smp;
+ /* real UID of the task */
+
kgid_t gid; /* real GID of the task */
kuid_t suid; /* saved UID of the task */
kgid_t sgid; /* saved GID of the task */
@@ -133,11 +143,6 @@ struct cred {
kuid_t fsuid; /* UID for VFS ops */
kgid_t fsgid; /* GID for VFS ops */
unsigned securebits; /* SUID-less security management */
- kernel_cap_t cap_inheritable; /* caps our children can inherit */
- kernel_cap_t cap_permitted; /* caps we're permitted */
- kernel_cap_t cap_effective; /* caps we can actually use */
- kernel_cap_t cap_bset; /* capability bounding set */
- kernel_cap_t cap_ambient; /* Ambient capability set */
#ifdef CONFIG_KEYS
unsigned char jit_keyring; /* default keyring to attach requested
* keys to */
@@ -152,7 +157,6 @@ struct cred {
struct user_struct *user; /* real user ID subscription */
struct user_namespace *user_ns; /* user_ns the caps and keyrings are relative to. */
struct group_info *group_info; /* supplementary groups for euid/fsgid */
- struct rcu_head rcu; /* RCU deletion hook */
};
extern void __put_cred(struct cred *);
next prev parent reply other threads:[~2015-10-28 0:14 UTC|newest]
Thread overview: 138+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-10-19 16:59 Fw: [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3) Stephen Hemminger
2015-10-19 23:33 ` Eric Dumazet
2015-10-20 1:12 ` Alan Burlison
2015-10-20 1:45 ` Eric Dumazet
2015-10-20 9:59 ` Alan Burlison
2015-10-20 11:24 ` David Miller
2015-10-20 11:39 ` Alan Burlison
2015-10-20 13:19 ` Fw: " Eric Dumazet
2015-10-20 13:45 ` Alan Burlison
2015-10-20 15:30 ` Eric Dumazet
2015-10-20 18:31 ` Alan Burlison
2015-10-20 18:42 ` Eric Dumazet
2015-10-21 10:25 ` David Laight
2015-10-21 10:49 ` Alan Burlison
2015-10-21 11:28 ` Eric Dumazet
2015-10-21 13:03 ` Alan Burlison
2015-10-21 13:29 ` Eric Dumazet
2015-10-21 3:49 ` Al Viro
2015-10-21 14:38 ` Alan Burlison
2015-10-21 15:30 ` David Miller
2015-10-21 16:04 ` Casper.Dik
2015-10-21 21:18 ` Eric Dumazet
2015-10-21 21:28 ` Al Viro
2015-10-21 16:32 ` Fw: " Eric Dumazet
2015-10-21 18:51 ` Al Viro
2015-10-21 20:33 ` Casper.Dik
2015-10-22 4:21 ` Al Viro
2015-10-22 10:55 ` Alan Burlison
2015-10-22 18:16 ` Al Viro
2015-10-22 20:15 ` Alan Burlison
2015-11-02 10:03 ` David Laight
2015-11-02 10:29 ` Al Viro
2015-10-21 22:28 ` Alan Burlison
2015-10-22 1:29 ` David Miller
2015-10-22 4:17 ` Alan Burlison
2015-10-22 4:44 ` Al Viro
2015-10-22 6:03 ` Al Viro
2015-10-22 6:34 ` Casper.Dik
2015-10-22 17:21 ` Al Viro
2015-10-22 18:24 ` Casper.Dik
2015-10-22 19:07 ` Al Viro
2015-10-22 19:51 ` Casper.Dik
2015-10-22 21:57 ` Al Viro
2015-10-23 9:52 ` Casper.Dik
2015-10-23 13:02 ` Eric Dumazet
2015-10-23 13:20 ` Casper.Dik
2015-10-23 13:48 ` Eric Dumazet
2015-10-23 14:13 ` Eric Dumazet
2015-10-23 13:35 ` Alan Burlison
2015-10-23 14:21 ` Eric Dumazet
2015-10-23 15:46 ` Alan Burlison
2015-10-23 16:00 ` Eric Dumazet
2015-10-23 16:07 ` Alan Burlison
2015-10-23 16:19 ` Eric Dumazet
2015-10-23 16:40 ` Alan Burlison
2015-10-23 17:47 ` Eric Dumazet
2015-10-23 17:59 ` [PATCH net-next] af_unix: do not report POLLOUT on listeners Eric Dumazet
2015-10-25 13:45 ` David Miller
2015-10-24 2:30 ` [Bug 106241] New: shutdown(3)/close(3) behaviour is incorrect for sockets in accept(3) Al Viro
2015-10-27 9:08 ` Casper.Dik
2015-10-27 10:52 ` Alan Burlison
2015-10-27 12:01 ` Eric Dumazet
2015-10-27 12:27 ` Alan Burlison
2015-10-27 12:44 ` Eric Dumazet
2015-10-27 13:42 ` David Miller
2015-10-27 13:37 ` Alan Burlison
2015-10-27 13:59 ` David Miller
2015-10-27 14:13 ` Alan Burlison
2015-10-27 14:39 ` David Miller
2015-10-27 14:39 ` Alan Burlison
2015-10-27 15:04 ` David Miller
2015-10-27 15:53 ` Alan Burlison
2015-10-27 23:17 ` Al Viro
2015-10-28 0:13 ` Eric Dumazet [this message]
2015-10-28 12:35 ` Al Viro
2015-10-28 13:24 ` Eric Dumazet
2015-10-28 14:47 ` Eric Dumazet
2015-10-28 21:13 ` Al Viro
2015-10-28 21:44 ` Eric Dumazet
2015-10-28 22:33 ` Al Viro
2015-10-28 23:08 ` Eric Dumazet
2015-10-29 0:15 ` Al Viro
2015-10-29 3:29 ` Eric Dumazet
2015-10-29 4:16 ` Al Viro
2015-10-29 12:35 ` Eric Dumazet
2015-10-29 13:48 ` Eric Dumazet
2015-10-30 17:18 ` Linus Torvalds
2015-10-30 21:02 ` Al Viro
2015-10-30 21:23 ` Linus Torvalds
2015-10-30 21:50 ` Linus Torvalds
2015-10-30 22:33 ` Al Viro
2015-10-30 23:52 ` Linus Torvalds
2015-10-31 0:09 ` Al Viro
2015-10-31 15:59 ` Eric Dumazet
2015-10-31 19:34 ` Al Viro
2015-10-31 19:54 ` Linus Torvalds
2015-10-31 20:29 ` Al Viro
2015-11-02 0:24 ` Al Viro
2015-11-02 0:59 ` Linus Torvalds
2015-11-02 2:14 ` Eric Dumazet
2015-11-02 6:22 ` Al Viro
2015-10-31 20:45 ` Eric Dumazet
2015-10-31 21:23 ` Linus Torvalds
2015-10-31 21:51 ` Al Viro
2015-10-31 22:34 ` Eric Dumazet
2015-10-31 1:07 ` Eric Dumazet
2015-10-28 16:04 ` Alan Burlison
2015-10-29 14:58 ` David Holland
2015-10-29 15:18 ` Alan Burlison
2015-10-29 16:01 ` David Holland
2015-10-29 16:15 ` Alan Burlison
2015-10-29 17:07 ` Al Viro
2015-10-29 17:12 ` Alan Burlison
2015-10-30 1:54 ` David Miller
2015-10-30 1:55 ` David Miller
2015-10-30 5:44 ` David Holland
2015-10-30 17:43 ` David Laight
2015-10-30 21:09 ` Al Viro
2015-11-04 15:54 ` David Laight
2015-11-04 16:27 ` Al Viro
2015-11-06 15:07 ` David Laight
2015-11-06 19:31 ` Al Viro
2015-10-22 6:51 ` Casper.Dik
2015-10-22 11:18 ` Alan Burlison
2015-10-22 11:15 ` Alan Burlison
2015-10-22 6:15 ` Casper.Dik
2015-10-22 11:30 ` Eric Dumazet
2015-10-22 11:58 ` Alan Burlison
2015-10-22 12:10 ` Eric Dumazet
2015-10-22 13:12 ` David Miller
2015-10-22 13:14 ` Alan Burlison
2015-10-22 17:05 ` Al Viro
2015-10-22 17:39 ` Alan Burlison
2015-10-22 18:56 ` Al Viro
2015-10-22 19:50 ` Casper.Dik
2015-10-23 17:09 ` Al Viro
2015-10-23 18:30 ` Fw: " David Holland
2015-10-23 19:51 ` Al Viro
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