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Date: Mon, 7 Apr 2008 14:47:45 -0300
From: Arnaldo Carvalho de Melo <acme@...hat.com>
To: Eric Dumazet <dada1@...mosbay.com>
Cc: Pavel Emelyanov <xemul@...nvz.org>,
Linux Netdev List <netdev@...r.kernel.org>,
Stephen Hemminger <shemminger@...tta.com>,
Patrick McHardy <kaber@...sh.net>
Subject: Re: [PATCH net-2.6.26 1/2] Shrink size of net_device by filling
alignment holes in it.
Em Mon, Apr 07, 2008 at 07:17:11PM +0200, Eric Dumazet escreveu:
> Eric Dumazet a écrit :
>> Pavel Emelyanov a écrit :
>>> I've found a much easier way to shrink the net_device structure rather
>>> that moving all the operations out of it. However, since
>>> the net_device may grow further, moving the operations into a
>>> separate place may look reasonable.
>>>
>>> The pahole tool showed, that there are a 124 and 80 bytes holes
>>> before the queue_lock and the _xmit_lock respectively. Moving most
>>> of the devices callbacks into the 2nd hole makes the sizeof of the
>>> structure be 1024 bytes.
>>>
>>>
>> On 32 bits platform and CONFIG_X86_L1_CACHE_SHIFT=7
>> I presume :)
>>
>> Could you check if x86_64 machines with X86_L1_CACHE_SHIFT = 7 or 8 dont
>> suffer from this patch ?
>>
>> At first glance I would say it seems OK, but this net_device is really
>> touchy for SMP performance :)
> I meant :
>
> X86_L1_CACHE_SHIFT = 6 (MK8 | MCORE2) or 7 (others)
Info _before_ Pavel's patch, not that big holes.
[acme@...pio linux-2.6]$ getconf LEVEL1_DCACHE_LINESIZE
64
model name : Intel(R) Core(TM)2 CPU T7200 @ 2.00GHz
[acme@...pio linux-2.6]$ grep X86_L1_CACHE_SHIFT /boot/config-`uname -r`
CONFIG_X86_L1_CACHE_SHIFT=6
[acme@...pio linux-2.6]$ pahole -C net_device ../build/linux-2.6/doppio/net/core/dev.o
struct net_device {
char name[16]; /* 0 16 */
struct hlist_node name_hlist; /* 16 16 */
long unsigned int mem_end; /* 32 8 */
long unsigned int mem_start; /* 40 8 */
long unsigned int base_addr; /* 48 8 */
unsigned int irq; /* 56 4 */
unsigned char if_port; /* 60 1 */
unsigned char dma; /* 61 1 */
/* XXX 2 bytes hole, try to pack */
/* --- cacheline 1 boundary (64 bytes) --- */
long unsigned int state; /* 64 8 */
struct list_head dev_list; /* 72 16 */
struct list_head napi_list; /* 88 16 */
int (*init)(struct net_device *); /* 104 8 */
long unsigned int features; /* 112 8 */
struct net_device * next_sched; /* 120 8 */
/* --- cacheline 2 boundary (128 bytes) --- */
int ifindex; /* 128 4 */
int iflink; /* 132 4 */
struct net_device_stats * (*get_stats)(struct net_device *); /* 136 8 */
struct net_device_stats stats; /* 144 184 */
/* --- cacheline 5 boundary (320 bytes) was 8 bytes ago --- */
const struct iw_handler_def * wireless_handlers; /* 328 8 */
struct iw_public_data * wireless_data; /* 336 8 */
const struct ethtool_ops * ethtool_ops; /* 344 8 */
const struct header_ops * header_ops; /* 352 8 */
unsigned int flags; /* 360 4 */
short unsigned int gflags; /* 364 2 */
short unsigned int priv_flags; /* 366 2 */
short unsigned int padded; /* 368 2 */
unsigned char operstate; /* 370 1 */
unsigned char link_mode; /* 371 1 */
unsigned int mtu; /* 372 4 */
short unsigned int type; /* 376 2 */
short unsigned int hard_header_len; /* 378 2 */
/* XXX 4 bytes hole, try to pack */
/* --- cacheline 6 boundary (384 bytes) --- */
struct net_device * master; /* 384 8 */
unsigned char perm_addr[32]; /* 392 32 */
unsigned char addr_len; /* 424 1 */
/* XXX 1 byte hole, try to pack */
short unsigned int dev_id; /* 426 2 */
/* XXX 4 bytes hole, try to pack */
struct dev_addr_list * uc_list; /* 432 8 */
int uc_count; /* 440 4 */
int uc_promisc; /* 444 4 */
/* --- cacheline 7 boundary (448 bytes) --- */
struct dev_addr_list * mc_list; /* 448 8 */
int mc_count; /* 456 4 */
int promiscuity; /* 460 4 */
int allmulti; /* 464 4 */
/* XXX 4 bytes hole, try to pack */
void * atalk_ptr; /* 472 8 */
void * ip_ptr; /* 480 8 */
void * dn_ptr; /* 488 8 */
void * ip6_ptr; /* 496 8 */
void * ec_ptr; /* 504 8 */
/* --- cacheline 8 boundary (512 bytes) --- */
void * ax25_ptr; /* 512 8 */
struct wireless_dev * ieee80211_ptr; /* 520 8 */
long unsigned int last_rx; /* 528 8 */
unsigned char dev_addr[32]; /* 536 32 */
unsigned char broadcast[32]; /* 568 32 */
/* --- cacheline 9 boundary (576 bytes) was 24 bytes ago --- */
spinlock_t ingress_lock; /* 600 4 */
/* XXX 4 bytes hole, try to pack */
struct Qdisc * qdisc_ingress; /* 608 8 */
/* XXX 24 bytes hole, try to pack */
/* --- cacheline 10 boundary (640 bytes) --- */
spinlock_t queue_lock; /* 640 4 */
/* XXX 4 bytes hole, try to pack */
struct Qdisc * qdisc; /* 648 8 */
struct Qdisc * qdisc_sleeping; /* 656 8 */
struct list_head qdisc_list; /* 664 16 */
long unsigned int tx_queue_len; /* 680 8 */
struct sk_buff * gso_skb; /* 688 8 */
/* XXX 8 bytes hole, try to pack */
/* --- cacheline 11 boundary (704 bytes) --- */
spinlock_t _xmit_lock; /* 704 4 */
int xmit_lock_owner; /* 708 4 */
void * priv; /* 712 8 */
int (*hard_start_xmit)(struct sk_buff *, struct net_device *); /* 720 8 */
long unsigned int trans_start; /* 728 8 */
int watchdog_timeo; /* 736 4 */
/* XXX 4 bytes hole, try to pack */
struct timer_list watchdog_timer; /* 744 80 */
/* XXX last struct has 4 bytes of padding */
/* XXX 8 bytes hole, try to pack */
/* --- cacheline 13 boundary (832 bytes) --- */
atomic_t refcnt; /* 832 4 */
/* XXX 4 bytes hole, try to pack */
struct list_head todo_list; /* 840 16 */
struct hlist_node index_hlist; /* 856 16 */
struct net_device * link_watch_next; /* 872 8 */
enum {
NETREG_UNINITIALIZED = 0,
NETREG_REGISTERED = 1,
NETREG_UNREGISTERING = 2,
NETREG_UNREGISTERED = 3,
NETREG_RELEASED = 4,
} reg_state; /* 880 4 */
/* XXX 4 bytes hole, try to pack */
void (*uninit)(struct net_device *); /* 888 8 */
/* --- cacheline 14 boundary (896 bytes) --- */
void (*destructor)(struct net_device *); /* 896 8 */
int (*open)(struct net_device *); /* 904 8 */
int (*stop)(struct net_device *); /* 912 8 */
void (*change_rx_flags)(struct net_device *, int); /* 920 8 */
void (*set_rx_mode)(struct net_device *); /* 928 8 */
void (*set_multicast_list)(struct net_device *); /* 936 8 */
int (*set_mac_address)(struct net_device *, void *); /* 944 8 */
int (*validate_addr)(struct net_device *); /* 952 8 */
/* --- cacheline 15 boundary (960 bytes) --- */
int (*do_ioctl)(struct net_device *, struct ifreq *, int); /* 960 8 */
int (*set_config)(struct net_device *, struct ifmap *); /* 968 8 */
int (*change_mtu)(struct net_device *, int); /* 976 8 */
void (*tx_timeout)(struct net_device *); /* 984 8 */
void (*vlan_rx_register)(struct net_device *, struct vlan_group *); /* 992 8 */
void (*vlan_rx_add_vid)(struct net_device *, short unsigned int); /* 1000 8 */
void (*vlan_rx_kill_vid)(struct net_device *, short unsigned int); /* 1008 8 */
int (*neigh_setup)(struct net_device *, struct neigh_parms *); /* 1016 8 */
/* --- cacheline 16 boundary (1024 bytes) --- */
struct netpoll_info * npinfo; /* 1024 8 */
void (*poll_controller)(struct net_device *); /* 1032 8 */
struct net * nd_net; /* 1040 8 */
struct net_bridge_port * br_port; /* 1048 8 */
struct macvlan_port * macvlan_port; /* 1056 8 */
struct device dev; /* 1064 584 */
/* --- cacheline 25 boundary (1600 bytes) was 48 bytes ago --- */
struct attribute_group * sysfs_groups[3]; /* 1648 24 */
/* --- cacheline 26 boundary (1664 bytes) was 8 bytes ago --- */
const struct rtnl_link_ops * rtnl_link_ops; /* 1672 8 */
unsigned int egress_subqueue_count; /* 1680 4 */
/* XXX 4 bytes hole, try to pack */
struct net_device_subqueue egress_subqueue[1]; /* 1688 8 */
/* size: 1728, cachelines: 27 */
/* sum members: 1617, holes: 14, sum holes: 79 */
/* padding: 32 */
/* paddings: 1, sum paddings: 4 */
};
Humm, I need to implement a way to inform pahole about fields that are
cacheline aligned, that together with --cacheline and --word_size would
allow us to try all these combinations, even --reorganize could use that
info...
- Arnaldo
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