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Yaffs ( Flash ) was designed and written by Charles Manning, of , , for the company Aleph One.
Yaffs1 was the first version of this file system and was designed for the then-current NAND chips with 512
page size (+ 16 byte spare (OOB;Out-Of-Band) area). Work started in 2002, and it was first released later that year. The initial work was sponsored by Toby Churchill Ltd, and Brightstar Engineering.
These older
also generally allow 2 or 3 write cycles per page. YAFFS takes advantage of this:
are marked by writing to a specific spare area byte. Newer NAND flash chips have larger pages, first 2K pages (+ 64 bytes OOB), later 4K, with stricter write requirements. Each page within an erase block (128 kilobytes) must be written to in sequential order, and each page must be written only once.[]
Designing a storage system that enforces a "write once rule" ("write once property") has several advantages.
YAFFS2 was designed to accommodate these newer chips. It was based on the YAFFS1 source code, with the major difference being that internal structures are not fixed to assume 512 byte sizing, and a block sequence number is placed on each written page. In this way older pages can be logically overwritten without violating the "write once" rule. It was released in late 2003.
YAFFS is a robust
that holds
as a high priority. A secondary YAFFS goal is high performance. YAFFS will typically outperform most alternatives. It is also designed to be portable and has been used on , , , , , and various special-purpose OSes. A variant 'YAFFS/Direct' is used in situations where there is no OS, embedded OSes or bootloaders: it has the same core filesystem but simpler interfacing to both the higher and lower level code and the NAND flash hardware.
The YAFFS codebase is licensed both under the
and under per-product licenses available from Aleph One.
There is no special procedure to
a YAFFS filesystem beyond simply erasing the flash memory. When a bad block is encountered, YAFFS follows the smart media scheme of marking the fifth byte of the block's spare area. Blocks marked as such remain unallocated from then on.[]
To write file data, YAFFS initially writes a whole page (chunk in YAFFS terminology) that describes the file , such as , name, path, etc. The new file is assigned a unique object ID every data chunk within the file will contain this unique object ID within the spare area. YAFFS maintains a tree structure in
of the physical location of these chunks. When a chunk is no longer valid (the file is deleted, or parts of the file are overwritten), YAFFS marks a particular byte in the spare area of the chunk as ‘dirty’. When an entire block (32 pages) is marked as dirty, YAFFS can erase the block and reclaim the space. When the filesystem's free space is low, YAFFS consolidates a group of good pages onto a new block. YAFFS then reclaims the space used by dirty pages within each of the original blocks.
When a YAFFS system
device, it must visit each block to check for valid data by scanning its spare area. With this information it then reconstitutes the memory-resident tree data structure.
YAFFS2 is similar in concept to YAFFS1, and shares m the YAFFS2 code base supports YAFFS1 data formats through backward compatibility. The main difference is that YAFFS2 needs to jump through significant hoops to meet the "write once" requirement of modern NAND flash.
YAFFS2 marks every newly written block with a sequence number that is . The sequence of the chunks can be inferred from the block sequence number and the chunk offset within the block. Thereby when YAFFS2 scans the flash and detects multiple chunks that have identical ObjectIDs and ChunkNumbers, it can choose which to use by taking the greatest sequence number. For efficiency reasons YAFFS2 also introduces the concept of shrink headers. For example, when a file is resized to a smaller size, YAFFS1 will mark all of the affected chunks as dirty - YAFFS2 cannot do this due to the "write once" rule. YAFFS2 instead writes a "shrink header", which indicates that a certain number of pages before that point are invalid. This lets YAFFS2 reconstruct the final state of the filesystem when the system reboots.
YAFFS2 uses a more abstract definition of the NAND flash allowing it to be used with a wider variety of flash parts with different geometries, bad block handling rules etc.
YAFFS2 later added support for , which bypasses normal mount scanning, allowing very fast mount times. Performance will vary, but mount times of 3 seconds for 2
have been reported.[]
Erasing a flash erase block sets all of its bits to 1s, and writing a write block (smaller than an erase block, but possibly bigger than a filesystem block) sets selected bits to 0s. One or two further writes to the block could be sustained if the bits being written to 0 were previously 1s in the write block. Writing a 0 to a bit which was already 0 risked making the 0 "stick", i.e. multiple erases could be needed to return the bit to a 1.[] Needless to say, this multiple-write practice was not generally tested and guaranteed by flash vendors, and cannot work at all on non- flash technologies.
Jack B. D Guang R. G and Vivek Sarkar. . p. 4
: A simple program to unpack YAFFS2 images.
: Utilities to create/extract a YAFFS2 image on Linux.
: Hidden categories:From Wikipedia, the free encyclopedia
The fifteenth edition of the
was held 22–30 August 2015 in , . 43 nations won medals, 144 of which were awarded.
topped the medal table for the first time, with 7 gold, 6 silver and 3 bronze medals. The
won 18 medals, six gold, six silver and six bronze, which was the highest tally. Host nation , finished 11th on the medals table, while
finished ninth.
205 IAAF member countries and territories participated, two more than in , with new IAAF member, , making its debut.
was also set to participate for the first time, but its sole athlete did not show up in Beijing.
won their first world title at these championships, with
winning the .
The event was the largest sporting event to take place at the
("Bird's Nest") since the .
When the seeking deadline passed on 15 March 2010, three candidate cities (,
and ) had confirmed their candidatures. London then withdrew citing that they didn't want to seem to be biased towards the bids for the Olympic Stadium by committing themselves to an athletics event, as the host for this event was to be announced before their 2011 stadium bid deadline. London then stated that they would bid for 2017 and had the blessing of the IAAF to do so. The IAAF announced Beijing as the winning candidate at the IAAF Council Meeting in
on 20 November 2010. The Council of IAAF approved the dates of 22 August until 30 August 2015.
Beijing National Stadium during the championships
Inside in daylight
Outside at night
The event was primarily held at the , which served as the athletics venue during the . Weather concerns prompted a reduction in capacity for the World Championships in A only the lower and middle tiers of the stadium were open, capping the venue at around 54,000 spectators rather than its capacity of 80,000. Tickets for the championships were available in three price categories, ranging from 50 RMB to 500 RMB.
Qualifiers
Semifinals
Chronology:
Chronology:
Chronology:
Chronology:
  *   Host nation
207 countries (or more accurately, IAAF members) with a total of 1,933 athletes were entered. Of those 1,771 athletes from 205 countries actually competed (thus excluding reserve athletes and non-starters). The biggest delegation was the one from the USA with 130 athletes. Two countries,
were set to participate, but none of their athletes showed up. The number of athletes per nation is shown in parentheses.
  (AFG) (1)
  (ALB) (1)
  (ALG) (14)
  (AND) (1)
  (ANG) (1)
  (AIA) (1)
  (ANT) (5)
  (ARG) (6)
  (ARM) (1)
  (ARU) (1)
  (AUS) (43)
  (AUT) (5)
  (AZE) (2)
  (BAH) (23)
  (BHR) (17)
  (BAN) (1)
  (BAR) (6)
  (BLR) (18)
  (BEL) (18)
  (BIZ) (1)
  (BEN) (1)
  (BER) (2)
  (BHU) (1)
  (BOL) (3)
  (BIH) (2)
  (BOT) (5)
  (BRA) (53)
  (IVB) (2)
  (BRU) (1)
  (BUL) (10)
  (BDI) (2)
  (BDI) (2)
  (CAM) (1)
  (CMR) (2)
  (CAN) (44)
  (CPV) (1)
  (CAY) (2)
  (CAF) (1)
  (CHA) (1)
  (CHI) (6)
  (CHN) (66)
  (COL) (12)
  (COM) (1)
  (CGO) (1)
  (COK) (1)
  (CRC) (2)
  (CRO) (6)
  (CUB) (24)
  (CYP) (3)
  (CZE) (25)
  (DEN) (3)
  (DJI) (3)
  (DMA) (1)
  (DOM) (6)
  (COD) (1)
  (ECU) (5)
  (EGY) (3)
  (ESA) (2)
  (GEQ) (1)
  (ERI) (9)
  (EST) (15)
  (ETH) (32)
  (FSM) (1)
  (FIJ) (2)
  (FIN) (17)
  (FRA) (36)
  (PYF) (1)
  (GEO) (1)
  (GER) (62)
  (GIB) (1)
  (GBR) (59)
  (GRE) (10)
  (GRN) (3)
  (GUM) (1)
  (GUA) (7)
  (GUI) (1)
  (GBS) (1)
  (GUY) (2)
  (HAI) (1)
  (HON) (1)
  (HKG) (1)
  (HUN) (12)
  (ISL) (2)
  (IND) (16)
  (INA) (1)
  (IRI) (5)
  (IRQ) (1)
  (IRL) (14)
  (ISR) (4)
  (ITA) (30)
  (CIV) (4)
  (JAM) (50)
  (JPN) (51)
  (JOR) (1)
  (KAZ) (10)
  (KEN) (52)
  (KIR) (1)
  (KOS) (1)
  (KUW) (1)
  (KGZ) (1)
  (LAO) (1)
  (LAT) (9)
  (LIB) (1)
  (LES) (2)
  (LBR) (1)
  (LBA) (1)
  (LTU) (11)
  (LUX) (2)
  (MAC) (1)
  (MKD) (1)
  (MAD) (1)
  (MAW) (1)
  (MAS) (1)
  (MDV) (1)
  (MLI) (1)
  (MLT) (1)
  (MTN) (1)
  (MRI) (1)
  (MEX) (5)
  (MDA) (4)
  (MON) (1)
  (MGL) (3)
  (MNE) (1)
  (MNT) (1)
  (MAR) (22)
  (MOZ) (1)
  (MYA) (1)
  (NAM) (2)
  (NRU) (1)
  (NEP) (1)
  (NED) (21)
  (NZL) (14)
  (NCA) (1)
  (NGR) (16)
  (PRK) (3)
  (NMI) (1)
  (NOR) (9)
  (OMN) (1)
  (PAK) (1)
  (PLW) (1)
  (PLE) (2)
  (PAN) (3)
  (PNG) (2)
  (PAR) (1)
  (PER) (6)
  (PHI) (1)
  (POL) (48)
  (POR) (16)
  (PUR) (3)
  (QAT) (6)
  (ROM) (16)
  (RUS) (62)
  (RWA) (1)
  (SKN) (3)
  (LCA) (2)
  (VIN) (1)
  (SAM) (2)
  (SMR) (1)
  (STP) (1)
  (KSA) (3)
  (SEN) (1)
  (SRB) (5)
  (SEY) (1)
  (SLE) (1)
  (SIN) (1)
  (SVK) (16)
  (SLO) (8)
  (SOL) (1)
  (SOM) (1)
  (RSA) (33)
  (KOR) (12)
  (ESP) (40)
  (SRI) (2)
  (SUD) (3)
  (SUR) (1)
  (SWZ) (1)
  (SWE) (24)
  (SUI) (15)
  (SYR) (2)
  (TPE) (5)
  (TJK) (2)
  (TAN) (4)
  (THA) (2)
  (GAM) (1)
  (TOG) (1)
  (TGA) (1)
  (TTO) (19)
  (TUN) (4)
  (TUR) (12)
  (TKM) (1)
  (TKS) (1)
  (TUV) (1)
  (UGA) (11)
  (UKR) (51)
  (UAE) (3)
  (USA) (130)
  (URU) (3)
  (UZB) (4)
  (VAN) (1)
  (VEN) (11)
  (VIE) (1)
  (ISV) (2)
  (YEM) (1)
  (ZAM) (2)
  (ZIM) (5)
As part of the event, the IAAF conducted a wide-reaching anti-doping programme. This included information-led targeted tests in the months previous to the championships and testing of athletes in and outside of competition during the championships. In total, the IAAF undertook 1405 instances of athlete doping controls in Beijing. This included 662 blood tests to inform the longitudinal athlete
programme, 161 blood tests specifically directed at identifying usage of either
stimulating agents (EPO), 54 out-of-competition urine tests and 528 urine tests conducted on-site (which also incorporates 239 for EPO analysis).
As was the case since the 2005 World Championships, athlete's doping samples were stored for future analysis, which could allow retrospective disqualifications via subsequent improvements to testing technology and methods. The number of tests was a new high for the event and the largest ever conducted by a sport-specific governing body at an event. The testing was undertaken in partnership with the
(CHINADA). An anti-doping education programme was also conducted, which included presentations on the risks of doping and a questionnaire designed by the .
Initial analysis identified two failed tests, both Kenyan women: hurdler
and sprinter . Both were disqualified immediately from the competition.
. BBC Sport. 20 November 2010.
from the original on 25 November .
. iaaf.org. .
. www.dothaneagle.com. 22 August 2015.[]
Monti, David. . competitor.com. Competitor Group 2015.
(PDF). Official Site. 12 July .
. iaaf.org. 15 March 2010.
. the Guardian.
. BBC News. 4 November 2010.
. insidethegames.biz.
. InsideTheGames.biz 2015.
. ticketing.iaafbeijing2015.com/. Archived from
on 27 September .
. iaaf.org.
. IAAF (). Retrieved on .
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