RFC - patch to reduce peak memory usage by disabling compression

["Øyvind Harboe" <oyvind.harboe@zylin.com>]

[-- Attachment #1: Type: text/plain, Size: 365 bytes --]

Rationale:

Reduce RAM usage by removing compression/decompression altogether.

Even trivial compression schemes require a working buffer,
hence all compression schemes and not only the most memory
hungry are removed.

I've introduced a define JFFS2_COMPRESS which is 1 in os-linux.h,
and which eCos can make configurable via its CDL files.



Øyvind

[-- Attachment #2: lessmem.txt --]
[-- Type: text/plain, Size: 4146 bytes --]

? lessmem.txt
Index: compr.c
===================================================================
RCS file: /home/cvs/mtd/fs/jffs2/compr.c,v
retrieving revision 1.26
diff -a -w -u -r1.26 compr.c
--- compr.c	12 Jan 2003 13:21:28 -0000	1.26
+++ compr.c	21 Aug 2003 12:26:50 -0000
@@ -28,6 +28,8 @@
 
 #include <linux/jffs2.h>
 
+#if defined(JFFS2_COMPRESS)
+
 int jffs2_zlib_compress(unsigned char *data_in, unsigned char *cpage_out, uint32_t *sourcelen, uint32_t *dstlen);
 void jffs2_zlib_decompress(unsigned char *data_in, unsigned char *cpage_out, uint32_t srclen, uint32_t destlen);
 int jffs2_rtime_compress(unsigned char *data_in, unsigned char *cpage_out, uint32_t *sourcelen, uint32_t *dstlen);
@@ -136,3 +138,5 @@
 	}
 	return 0;
 }
+
+#endif
Index: gc.c
===================================================================
RCS file: /home/cvs/mtd/fs/jffs2/gc.c,v
retrieving revision 1.103
diff -a -w -u -r1.103 gc.c
--- gc.c	22 May 2003 18:01:02 -0000	1.103
+++ gc.c	21 Aug 2003 12:26:51 -0000
@@ -1085,9 +1085,11 @@
 
 		writebuf = pg_ptr + (offset & (PAGE_CACHE_SIZE -1));
 
+#if defined(JFFS2_COMPRESS)
 		if (comprbuf) {
 			comprtype = jffs2_compress(writebuf, comprbuf, &datalen, &cdatalen);
 		}
+#endif
 		if (comprtype) {
 			writebuf = comprbuf;
 		} else {
Index: os-linux.h
===================================================================
RCS file: /home/cvs/mtd/fs/jffs2/os-linux.h,v
retrieving revision 1.28
diff -a -w -u -r1.28 os-linux.h
--- os-linux.h	2 Jul 2003 10:46:00 -0000	1.28
+++ os-linux.h	21 Aug 2003 12:26:51 -0000
@@ -189,6 +189,12 @@
 /* super.c */
 
 
+// by disabling compression, some working memory can be saved.
+// for embedded systems(e.g. eCos) even 50k ram is substantial
+// note that all forms of compression is disabled, since even
+// simple run-length encoding allocates working space.
+#define JFFS2_COMPRESS 1
+
 #endif /* __JFFS2_OS_LINUX_H__ */
 
 
Index: read.c
===================================================================
RCS file: /home/cvs/mtd/fs/jffs2/read.c,v
retrieving revision 1.33
diff -a -w -u -r1.33 read.c
--- read.c	17 Jul 2003 08:44:12 -0000	1.33
+++ read.c	21 Aug 2003 12:26:51 -0000
@@ -93,6 +93,7 @@
 		}
 	}
 	if (ri->compr != JFFS2_COMPR_NONE) {
+#if defined(JFFS2_COMPRESS)
 		if (len < je32_to_cpu(ri->dsize)) {
 			decomprbuf = kmalloc(je32_to_cpu(ri->dsize), GFP_KERNEL);
 			if (!decomprbuf) {
@@ -102,6 +103,10 @@
 		} else {
 			decomprbuf = buf;
 		}
+#else
+		ret = -EINVAL;
+		goto out_readbuf;
+#endif
 	} else {
 		decomprbuf = readbuf;
 	}
@@ -124,6 +129,8 @@
 		goto out_decomprbuf;
 	}
 	D2(printk(KERN_DEBUG "Data CRC matches calculated CRC %08x\n", crc));
+
+#if defined(JFFS2_COMPRESS)
 	if (ri->compr != JFFS2_COMPR_NONE) {
 		D2(printk(KERN_DEBUG "Decompress %d bytes from %p to %d bytes at %p\n",
 			  je32_to_cpu(ri->csize), readbuf, je32_to_cpu(ri->dsize), decomprbuf)); 
@@ -133,7 +140,7 @@
 			goto out_decomprbuf;
 		}
 	}
-
+#endif
 	if (len < je32_to_cpu(ri->dsize)) {
 		memcpy(buf, decomprbuf+ofs, len);
 	}
Index: write.c
===================================================================
RCS file: /home/cvs/mtd/fs/jffs2/write.c,v
retrieving revision 1.65
diff -a -w -u -r1.65 write.c
--- write.c	21 Jan 2003 18:11:29 -0000	1.65
+++ write.c	21 Aug 2003 12:26:51 -0000
@@ -300,6 +300,7 @@
 		datalen = writelen;
 		cdatalen = min_t(uint32_t, alloclen - sizeof(*ri), writelen);
 
+#if defined(JFFS2_COMPRESS)
 		comprbuf = kmalloc(cdatalen, GFP_KERNEL);
 		if (comprbuf) {
 			comprtype = jffs2_compress(buf, comprbuf, &datalen, &cdatalen);
@@ -308,9 +309,12 @@
 			/* Either compression failed, or the allocation of comprbuf failed */
 			if (comprbuf)
 				kfree(comprbuf);
+#endif
 			comprbuf = buf;
 			datalen = cdatalen;
+#if defined(CYGPKG_FS_JFFS2_COMPRESS)
 		}
+#endif
 		/* Now comprbuf points to the data to be written, be it compressed or not.
 		   comprtype holds the compression type, and comprtype == JFFS2_COMPR_NONE means
 		   that the comprbuf doesn't need to be kfree()d.