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SubjectRe: [PATCH] Breaking down the global IPC locks - 2.5.31
mingming cao wrote:
>
> This patch breaks the three global IPC locks into one lock per IPC ID.
> By doing so it could reduce possible lock contention in workloads which
> make heavy use of IPC semaphores, message queues and Shared
> memories...etc.

Here is the patch again. Fixed a typo. *_^diff -urN -X ../dontdiff ../base/linux-2.5.31/include/linux/ipc.h 2.5.31-ipc/include/linux/ipc.h
--- ../base/linux-2.5.31/include/linux/ipc.h Sat Aug 10 18:41:16 2002
+++ 2.5.31-ipc/include/linux/ipc.h Tue Aug 13 10:23:59 2002
@@ -56,6 +56,7 @@
/* used by in-kernel data structures */
struct kern_ipc_perm
{
+ spinlock_t lock;
key_t key;
uid_t uid;
gid_t gid;
diff -urN -X ../dontdiff ../base/linux-2.5.31/ipc/util.c 2.5.31-ipc/ipc/util.c
--- ../base/linux-2.5.31/ipc/util.c Sat Aug 10 18:41:27 2002
+++ 2.5.31-ipc/ipc/util.c Wed Aug 14 15:59:19 2002
@@ -74,7 +74,7 @@
printk(KERN_ERR "ipc_init_ids() failed, ipc service disabled.\n");
ids->size = 0;
}
- ids->ary = SPIN_LOCK_UNLOCKED;
+ ids->ary =RW_LOCK_UNLOCKED;
for(i=0;i<ids->size;i++)
ids->entries[i].p = NULL;
}
@@ -120,13 +120,13 @@
for(i=ids->size;i<newsize;i++) {
new[i].p = NULL;
}
- spin_lock(&ids->ary);
+ write_lock(&ids->ary);

old = ids->entries;
ids->entries = new;
i = ids->size;
ids->size = newsize;
- spin_unlock(&ids->ary);
+ write_unlock(&ids->ary);
ipc_free(old, sizeof(struct ipc_id)*i);
return ids->size;
}
@@ -165,7 +165,9 @@
if(ids->seq > ids->seq_max)
ids->seq = 0;

- spin_lock(&ids->ary);
+ new->lock = SPIN_LOCK_UNLOCKED;
+ read_lock(&ids->ary);
+ spin_lock(&new->lock);
ids->entries[id].p = new;
return id;
}
diff -urN -X ../dontdiff ../base/linux-2.5.31/ipc/util.h 2.5.31-ipc/ipc/util.h
--- ../base/linux-2.5.31/ipc/util.h Sat Aug 10 18:41:40 2002
+++ 2.5.31-ipc/ipc/util.h Wed Aug 14 17:05:22 2002
@@ -19,7 +19,7 @@
unsigned short seq;
unsigned short seq_max;
struct semaphore sem;
- spinlock_t ary;
+ rwlock_t ary;
struct ipc_id* entries;
};

@@ -47,7 +47,7 @@

extern inline void ipc_lockall(struct ipc_ids* ids)
{
- spin_lock(&ids->ary);
+ write_lock(&ids->ary);
}

extern inline struct kern_ipc_perm* ipc_get(struct ipc_ids* ids, int id)
@@ -63,7 +63,7 @@

extern inline void ipc_unlockall(struct ipc_ids* ids)
{
- spin_unlock(&ids->ary);
+ write_unlock(&ids->ary);
}
extern inline struct kern_ipc_perm* ipc_lock(struct ipc_ids* ids, int id)
{
@@ -72,16 +72,29 @@
if(lid >= ids->size)
return NULL;

- spin_lock(&ids->ary);
+ read_lock(&ids->ary);
out = ids->entries[lid].p;
- if(out==NULL)
- spin_unlock(&ids->ary);
+ if(out==NULL) {
+ read_unlock(&ids->ary);
+ return NULL;
+ }
+ spin_lock(&out->lock);
return out;
}

extern inline void ipc_unlock(struct ipc_ids* ids, int id)
{
- spin_unlock(&ids->ary);
+ int lid = id % SEQ_MULTIPLIER;
+ struct kern_ipc_perm* out;
+
+ if(lid >= ids->size)
+ return;
+ out = ids->entries[lid].p;
+ if (out == NULL)
+ return;
+
+ spin_unlock(&out->lock);
+ read_unlock(&ids->ary);
}

extern inline int ipc_buildid(struct ipc_ids* ids, int id, int seq)
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