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authorWilliam Cohen <wcohen@redhat.com>2007-05-08 00:23:41 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 11:14:58 -0700
commit97dc32cdb1b53832801159d5f634b41aad9d0a23 (patch)
tree438f59c84d3528de5f68583d312beceb1aa32659 /include/linux/sched.h
parent4d7bf11d649c72621ca31b8ea12b9c94af380e63 (diff)
reduce size of task_struct on 64-bit machines
This past week I was playing around with that pahole tool (http://oops.ghostprotocols.net:81/acme/dwarves/) and looking at the size of various struct in the kernel. I was surprised by the size of the task_struct on x86_64, approaching 4K. I looked through the fields in task_struct and found that a number of them were declared as "unsigned long" rather than "unsigned int" despite them appearing okay as 32-bit sized fields. On x86_64 "unsigned long" ends up being 8 bytes in size and forces 8 byte alignment. Is there a reason there a reason they are "unsigned long"? The patch below drops the size of the struct from 3808 bytes (60 64-byte cachelines) to 3760 bytes (59 64-byte cachelines). A couple other fields in the task struct take a signficant amount of space: struct thread_struct thread; 688 struct held_lock held_locks[30]; 1680 CONFIG_LOCKDEP is turned on in the .config [akpm@linux-foundation.org: fix printk warnings] Cc: <linux-arch@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include/linux/sched.h')
-rw-r--r--include/linux/sched.h12
1 files changed, 6 insertions, 6 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h
index a1707583de4..d9acbbb39f9 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -801,8 +801,8 @@ struct task_struct {
volatile long state; /* -1 unrunnable, 0 runnable, >0 stopped */
struct thread_info *thread_info;
atomic_t usage;
- unsigned long flags; /* per process flags, defined below */
- unsigned long ptrace;
+ unsigned int flags; /* per process flags, defined below */
+ unsigned int ptrace;
int lock_depth; /* BKL lock depth */
@@ -825,7 +825,7 @@ struct task_struct {
unsigned long long sched_time; /* sched_clock time spent running */
enum sleep_type sleep_type;
- unsigned long policy;
+ unsigned int policy;
cpumask_t cpus_allowed;
unsigned int time_slice, first_time_slice;
@@ -845,11 +845,11 @@ struct task_struct {
/* task state */
struct linux_binfmt *binfmt;
- long exit_state;
+ int exit_state;
int exit_code, exit_signal;
int pdeath_signal; /* The signal sent when the parent dies */
/* ??? */
- unsigned long personality;
+ unsigned int personality;
unsigned did_exec:1;
pid_t pid;
pid_t tgid;
@@ -881,7 +881,7 @@ struct task_struct {
int __user *set_child_tid; /* CLONE_CHILD_SETTID */
int __user *clear_child_tid; /* CLONE_CHILD_CLEARTID */
- unsigned long rt_priority;
+ unsigned int rt_priority;
cputime_t utime, stime;
unsigned long nvcsw, nivcsw; /* context switch counts */
struct timespec start_time;