Burst read and other improvements

Joakim Tjernlund Joakim.Tjernlund at lumentis.se
Mon Dec 17 08:08:17 EST 2001

Hi all

Previously I reported that enabling burst read on Flash did not improve 
performance. That's not true :-(

I have measured the mount time with  this command:
time mount /dev/mtdblock4 /jffs2/
(Currently I am mostly intressted in lowering my mount times)

Here is what I get:
No optimization:  10.51 s.
with burst read:  9.12 s.
as above + patch to scan.c: 8.29 s
as above + #define  ACCT_PARANOIA_CHECK(jeb)  to nothing: 7.95 s.

This is on a MPC860 cpu at 80MHz and 40 MHz bus speed. 
   Is the ACCT_PARANOIA_CHECK still needed?

   Does anybody else get better mount times by patching scan.c?
   Would be nice if this patch could make it into CVS ...


patch to scan.c:
--- scan.c      2001/10/25 12:11:11     1.4
+++ scan.c      2001/12/17 12:43:36
@@ -334,7 +334,7 @@
        __u32 scanlen = (jeb->offset + c->sector_size) - *startofs;
        __u32 curofs = *startofs;
-       buf = kmalloc(min((__u32)PAGE_SIZE, scanlen), GFP_KERNEL);
+       buf = kmalloc(min((__u32)PAGE_SIZE/4, scanlen), GFP_KERNEL);
        if (!buf) {
                printk(KERN_WARNING "Scan buffer allocation failed\n");
                return -ENOMEM;
@@ -343,7 +343,7 @@
                ssize_t retlen;
                int ret, i;
-               ret = c->mtd->read(c->mtd, curofs, min((__u32)PAGE_SIZE, 
scanlen), &retlen, (char *)buf);
+               ret = c->mtd->read(c->mtd, curofs, min((__u32)PAGE_SIZE/4, 
scanlen), &retlen, (char *)buf);
                if(ret) {
                        D1(printk(KERN_WARNING "jffs2_scan_empty(): Read 0x%x 
bytes at 0x%08x returned %d\n", min((__u32)PAGE_SIZE, scanlen), curofs, ret));


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