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Subject[PATCH] SysV IPC loop speedups, kernel 2.4.3
This patch contains a couple of micro-optimizations for the loops in
ipc/msg.c's load_msg() and store_msg(). It works fine for me under
2.4.3.

--
-------------------------+--------------------------------------------
R H L U Scott Maxwell: | ``Life results from the non-random survival
E A I X maxwell@ | of randomly varying replicators.''
D T N 6 ScottMaxwell.org | -- Richard Dawkinsdiff -urN linux-2.4.3/ipc/msg.c linux/ipc/msg.c
--- linux-2.4.3/ipc/msg.c Mon Feb 19 10:18:18 2001
+++ linux/ipc/msg.c Tue Apr 17 22:34:36 2001
@@ -177,28 +177,30 @@
goto out_err;
}

- len -= alen;
- src = ((char*)src)+alen;
- pseg = &msg->next;
- while(len > 0) {
- struct msg_msgseg* seg;
- alen = len;
- if(alen > DATALEN_SEG)
- alen = DATALEN_SEG;
- seg = (struct msg_msgseg *) kmalloc (sizeof(*seg) + alen, GFP_KERNEL);
- if(seg==NULL) {
- err=-ENOMEM;
- goto out_err;
- }
- *pseg = seg;
- seg->next = NULL;
- if(copy_from_user (seg+1, src, alen)) {
- err = -EFAULT;
- goto out_err;
+ if (len > DATALEN_MSG) {
+ pseg = &msg->next;
+ while(len > alen) {
+ struct msg_msgseg* seg;
+
+ len -= alen;
+ src = ((char*)src)+alen;
+
+ alen = len;
+ if(alen > DATALEN_SEG)
+ alen = DATALEN_SEG;
+ seg = (struct msg_msgseg *) kmalloc (sizeof(*seg) + alen, GFP_KERNEL);
+ if(seg==NULL) {
+ err=-ENOMEM;
+ goto out_err;
+ }
+ *pseg = seg;
+ seg->next = NULL;
+ if(copy_from_user (seg+1, src, alen)) {
+ err = -EFAULT;
+ goto out_err;
+ }
+ pseg = &seg->next;
}
- pseg = &seg->next;
- len -= alen;
- src = ((char*)src)+alen;
}
return msg;

@@ -218,18 +220,20 @@
if(copy_to_user (dest, msg+1, alen))
return -1;

- len -= alen;
- dest = ((char*)dest)+alen;
- seg = msg->next;
- while(len > 0) {
- alen = len;
- if(alen > DATALEN_SEG)
- alen = DATALEN_SEG;
- if(copy_to_user (dest, seg+1, alen))
- return -1;
- len -= alen;
- dest = ((char*)dest)+alen;
- seg=seg->next;
+ if (len > DATALEN_MSG) {
+ seg = msg->next;
+ while(len > alen) {
+ len -= alen;
+ dest = ((char*)dest)+alen;
+
+ alen = len;
+ if(alen > DATALEN_SEG)
+ alen = DATALEN_SEG;
+ if(copy_to_user (dest, seg+1, alen))
+ return -1;
+
+ seg=seg->next;
+ }
}
return 0;
}
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