yaffs2.html

FAT32文件系统详细介绍

			<TD WIDTH=20% VALIGN=TOP>
				<P>Program</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="800" SDNUM="5129;">
				<P ALIGN=RIGHT>800</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="800" SDNUM="5129;">
				<P ALIGN=RIGHT>800</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="200" SDNUM="5129;">
				<P ALIGN=RIGHT>200</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="200" SDNUM="5129;">
				<P ALIGN=RIGHT>200</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Seek</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="40" SDNUM="5129;">
				<P ALIGN=RIGHT>40</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="40" SDNUM="5129;">
				<P ALIGN=RIGHT>40</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="10" SDNUM="5129;">
				<P ALIGN=RIGHT>10</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="10" SDNUM="5129;">
				<P ALIGN=RIGHT>10</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Read</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="220" SDNUM="5129;">
				<P ALIGN=RIGHT>220</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="220" SDNUM="5129;">
				<P ALIGN=RIGHT>220</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="220" SDNUM="5129;">
				<P ALIGN=RIGHT>220</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="110" SDNUM="5129;">
				<P ALIGN=RIGHT>110</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Total</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1320" SDNUM="5129;">
				<P ALIGN=RIGHT>1320</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1320" SDNUM="5129;">
				<P ALIGN=RIGHT>1320</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="660" SDNUM="5129;">
				<P ALIGN=RIGHT>660</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="440" SDNUM="5129;">
				<P ALIGN=RIGHT>440</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>MB/s</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1.5" SDNUM="5129;">
				<P ALIGN=RIGHT>1.5</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1.5" SDNUM="5129;">
				<P ALIGN=RIGHT>1.5</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="3" SDNUM="5129;">
				<P ALIGN=RIGHT>3</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="4.5" SDNUM="5129;">
				<P ALIGN=RIGHT>4.5</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Relative speed</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1" SDNUM="5129;">
				<P ALIGN=RIGHT>1</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1" SDNUM="5129;">
				<P ALIGN=RIGHT>1</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="2" SDNUM="5129;">
				<P ALIGN=RIGHT>2</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="3" SDNUM="5129;">
				<P ALIGN=RIGHT>3</P>
			</TD>
		</TR>
	</TBODY>
</TABLE>
<P><BR><BR>
</P>
<P>Times for 1MB delete (units of 1uS).</P>
<TABLE WIDTH=100% BORDER=1 CELLPADDING=4 CELLSPACING=3>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<THEAD>
		<TR VALIGN=TOP>
			<TH WIDTH=20%>
				<P>Operation</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS1</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS2 (512b pages)</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS2 (2kB pages)</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS2(2kB pages, x16)</P>
			</TH>
		</TR>
	</THEAD>
	<TBODY>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Seek</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="20480" SDNUM="5129;">
				<P ALIGN=RIGHT>20480</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="0" SDNUM="5129;">
				<P ALIGN=RIGHT>0</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="0" SDNUM="5129;">
				<P ALIGN=RIGHT>0</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="0" SDNUM="5129;">
				<P ALIGN=RIGHT>0</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Program</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="409600" SDNUM="5129;">
				<P ALIGN=RIGHT>409600</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="0" SDNUM="5129;">
				<P ALIGN=RIGHT>0</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="0" SDNUM="5129;">
				<P ALIGN=RIGHT>0</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="0" SDNUM="5129;">
				<P ALIGN=RIGHT>0</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Erase</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="128000" SDNUM="5129;">
				<P ALIGN=RIGHT>128000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="128000" SDNUM="5129;">
				<P ALIGN=RIGHT>128000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="16000" SDNUM="5129;">
				<P ALIGN=RIGHT>16000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="16000" SDNUM="5129;">
				<P ALIGN=RIGHT>16000</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Total</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="558080" SDNUM="5129;">
				<P ALIGN=RIGHT>558080</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="128000" SDNUM="5129;">
				<P ALIGN=RIGHT>128000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="16000" SDNUM="5129;">
				<P ALIGN=RIGHT>16000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="16000" SDNUM="5129;">
				<P ALIGN=RIGHT>16000</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>MB/s</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1.8" SDNUM="5129;">
				<P ALIGN=RIGHT>1.8</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="7.8" SDNUM="5129;">
				<P ALIGN=RIGHT>7.8</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="62.5" SDNUM="5129;">
				<P ALIGN=RIGHT>62.5</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="62.5" SDNUM="5129;">
				<P ALIGN=RIGHT>62.5</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Relative speed</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1" SDNUM="5129;">
				<P ALIGN=RIGHT>1</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="4" SDNUM="5129;">
				<P ALIGN=RIGHT>4</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="34" SDNUM="5129;">
				<P ALIGN=RIGHT>34</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="34" SDNUM="5129;">
				<P ALIGN=RIGHT>34</P>
			</TD>
		</TR>
	</TBODY>
</TABLE>
<P><BR><BR>
</P>
<P>Times for 1MB of garbage collection at 50% dirty (units of 1uS).</P>
<TABLE WIDTH=100% BORDER=1 CELLPADDING=4 CELLSPACING=3>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<COL WIDTH=51*>
	<THEAD>
		<TR VALIGN=TOP>
			<TH WIDTH=20%>
				<P>Operation</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS1</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS2 (512b pages)</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS2 (2kB pages)</P>
			</TH>
			<TH WIDTH=20%>
				<P>YAFFS2(2kB pages, x16)</P>
			</TH>
		</TR>
	</THEAD>
	<TBODY>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Delete 1MB</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="558080" SDNUM="5129;">
				<P ALIGN=RIGHT>558080</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="128000" SDNUM="5129;">
				<P ALIGN=RIGHT>128000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="16000" SDNUM="5129;">
				<P ALIGN=RIGHT>16000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="16000" SDNUM="5129;">
				<P ALIGN=RIGHT>16000</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Write 0.5MB</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="337920" SDNUM="5129;">
				<P ALIGN=RIGHT>337920</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="337920" SDNUM="5129;">
				<P ALIGN=RIGHT>337920</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="168960" SDNUM="5129;">
				<P ALIGN=RIGHT>168960</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="112640" SDNUM="5129;">
				<P ALIGN=RIGHT>112640</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Total</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="896000" SDNUM="5129;">
				<P ALIGN=RIGHT>896000</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="465920" SDNUM="5129;">
				<P ALIGN=RIGHT>465920</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="184960" SDNUM="5129;">
				<P ALIGN=RIGHT>184960</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="128640" SDNUM="5129;">
				<P ALIGN=RIGHT>128640</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>MB/s</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1.1" SDNUM="5129;">
				<P ALIGN=RIGHT>1.1</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="2.1" SDNUM="5129;">
				<P ALIGN=RIGHT>2.1</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="5.4" SDNUM="5129;">
				<P ALIGN=RIGHT>5.4</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="7.7" SDNUM="5129;">
				<P ALIGN=RIGHT>7.7</P>
			</TD>
		</TR>
		<TR>
			<TD WIDTH=20% VALIGN=TOP>
				<P>Relative speed</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1" SDNUM="5129;">
				<P ALIGN=RIGHT>1</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="1.9" SDNUM="5129;">
				<P ALIGN=RIGHT>1.9</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="4.9" SDNUM="5129;">
				<P ALIGN=RIGHT>4.9</P>
			</TD>
			<TD WIDTH=20% VALIGN=BOTTOM SDVAL="7" SDNUM="5129;">
				<P ALIGN=RIGHT>7</P>
			</TD>
		</TR>
	</TBODY>
</TABLE>
<P><BR><BR>
</P>
<H2>MTD Interface</H2>
<P>As mentioned before, YAFFS2 requires a chunk-size of at least 1kB
to get a large enough spare area to support the increased size of the
tags. This is not really a disadvantage, but should rather be viewed
as an opportunity to exploit the NAND hardware more effectively. In
particular:</P>
<UL>
	<LI><P>Newer, larger, NAND with 2kB pages can be used in chunks of
	2kB. Keeping the relationship of one chunk per page improves
	robustness and performance (rather than say trying to &quot;fake&quot;
	512byte  pages). A block comprises 64x2kB pages.</P>
	<LI><P>Some devices have 512byte pages, but are arranged as multiple
	&quot;bit planes&quot; which can be programmed and erased in
	parallel. For example, the Samsung K9K1G08U0M can support 4
	simultaneous operations. YAFFS2 can exploit this by using 2kB chunks
	 by using  groups of 4 pages - one on each bitplane. Virtual blocks
	would be built which comprise 32x2kB chunks.</P>
</UL>
<P>To this end, yaffs_guts is being re-crafted to support arbitrary
chunk size (power of 2, &gt;= 1024), with arbitrary block size.</P>
<P>Currently, YAFFS also makes some other assumptions which will need
to be changed:</P>
<UL>
	<LI><P>Spare layout. Might need to be changed. This is relatively
	simple to shuffle around.</P>
	<LI><P>Bad block detection. Currently YAFFS uses the SmartMedia
	detection (checks first two pages for bad block markers). Needs to
	be more flexible. eg. Sandisk/Toshiba MLC parts mark the last two
	pages in a block.</P>
	<LI><P>ECC was on this list, but now seems flexible enough. Thanx
	Thomas.</P>
</UL>
<P>Some of these differences can be absorbed in the yaffs_mtd layer.
Some will need to be handles inside the mtd itself.</P>
<P>$Id: yaffs2.html,v 1.2 2003/01/14 23:15:41 charles Exp $</P>
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