diff options
Diffstat (limited to 'Documentation')
| -rw-r--r-- | Documentation/DMA-API-HOWTO.txt (renamed from Documentation/PCI/PCI-DMA-mapping.txt) | 0 | ||||
| -rw-r--r-- | Documentation/cgroups/memory.txt | 2 | ||||
| -rw-r--r-- | Documentation/circular-buffers.txt | 234 | ||||
| -rw-r--r-- | Documentation/connector/cn_test.c | 1 | ||||
| -rw-r--r-- | Documentation/filesystems/00-INDEX | 2 | ||||
| -rw-r--r-- | Documentation/filesystems/9p.txt | 18 | ||||
| -rw-r--r-- | Documentation/filesystems/ceph.txt | 11 | ||||
| -rw-r--r-- | Documentation/filesystems/tmpfs.txt | 6 | ||||
| -rw-r--r-- | Documentation/memory-barriers.txt | 20 | ||||
| -rw-r--r-- | Documentation/powerpc/dts-bindings/fsl/cpm_qe/qe.txt | 54 | ||||
| -rw-r--r-- | Documentation/volatile-considered-harmful.txt | 6 |
11 files changed, 342 insertions, 12 deletions
diff --git a/Documentation/PCI/PCI-DMA-mapping.txt b/Documentation/DMA-API-HOWTO.txt index 52618ab069a..52618ab069a 100644 --- a/Documentation/PCI/PCI-DMA-mapping.txt +++ b/Documentation/DMA-API-HOWTO.txt diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt index f8bc802d70b..3a6aecd078b 100644 --- a/Documentation/cgroups/memory.txt +++ b/Documentation/cgroups/memory.txt @@ -340,7 +340,7 @@ Note: 5.3 swappiness Similar to /proc/sys/vm/swappiness, but affecting a hierarchy of groups only. - Following cgroups' swapiness can't be changed. + Following cgroups' swappiness can't be changed. - root cgroup (uses /proc/sys/vm/swappiness). - a cgroup which uses hierarchy and it has child cgroup. - a cgroup which uses hierarchy and not the root of hierarchy. diff --git a/Documentation/circular-buffers.txt b/Documentation/circular-buffers.txt new file mode 100644 index 00000000000..8117e5bf606 --- /dev/null +++ b/Documentation/circular-buffers.txt @@ -0,0 +1,234 @@ + ================ + CIRCULAR BUFFERS + ================ + +By: David Howells <dhowells@redhat.com> + Paul E. McKenney <paulmck@linux.vnet.ibm.com> + + +Linux provides a number of features that can be used to implement circular +buffering. There are two sets of such features: + + (1) Convenience functions for determining information about power-of-2 sized + buffers. + + (2) Memory barriers for when the producer and the consumer of objects in the + buffer don't want to share a lock. + +To use these facilities, as discussed below, there needs to be just one +producer and just one consumer. It is possible to handle multiple producers by +serialising them, and to handle multiple consumers by serialising them. + + +Contents: + + (*) What is a circular buffer? + + (*) Measuring power-of-2 buffers. + + (*) Using memory barriers with circular buffers. + - The producer. + - The consumer. + + +========================== +WHAT IS A CIRCULAR BUFFER? +========================== + +First of all, what is a circular buffer? A circular buffer is a buffer of +fixed, finite size into which there are two indices: + + (1) A 'head' index - the point at which the producer inserts items into the + buffer. + + (2) A 'tail' index - the point at which the consumer finds the next item in + the buffer. + +Typically when the tail pointer is equal to the head pointer, the buffer is +empty; and the buffer is full when the head pointer is one less than the tail +pointer. + +The head index is incremented when items are added, and the tail index when +items are removed. The tail index should never jump the head index, and both +indices should be wrapped to 0 when they reach the end of the buffer, thus +allowing an infinite amount of data to flow through the buffer. + +Typically, items will all be of the same unit size, but this isn't strictly +required to use the techniques below. The indices can be increased by more +than 1 if multiple items or variable-sized items are to be included in the +buffer, provided that neither index overtakes the other. The implementer must +be careful, however, as a region more than one unit in size may wrap the end of +the buffer and be broken into two segments. + + +============================ +MEASURING POWER-OF-2 BUFFERS +============================ + +Calculation of the occupancy or the remaining capacity of an arbitrarily sized +circular buffer would normally be a slow operation, requiring the use of a +modulus (divide) instruction. However, if the buffer is of a power-of-2 size, +then a much quicker bitwise-AND instruction can be used instead. + +Linux provides a set of macros for handling power-of-2 circular buffers. These +can be made use of by: + + #include <linux/circ_buf.h> + +The macros are: + + (*) Measure the remaining capacity of a buffer: + + CIRC_SPACE(head_index, tail_index, buffer_size); + + This returns the amount of space left in the buffer[1] into which items + can be inserted. + + + (*) Measure the maximum consecutive immediate space in a buffer: + + CIRC_SPACE_TO_END(head_index, tail_index, buffer_size); + + This returns the amount of consecutive space left in the buffer[1] into + which items can be immediately inserted without having to wrap back to the + beginning of the buffer. + + + (*) Measure the occupancy of a buffer: + + CIRC_CNT(head_index, tail_index, buffer_size); + + This returns the number of items currently occupying a buffer[2]. + + + (*) Measure the non-wrapping occupancy of a buffer: + + CIRC_CNT_TO_END(head_index, tail_index, buffer_size); + + This returns the number of consecutive items[2] that can be extracted from + the buffer without having to wrap back to the beginning of the buffer. + + +Each of these macros will nominally return a value between 0 and buffer_size-1, +however: + + [1] CIRC_SPACE*() are intended to be used in the producer. To the producer + they will return a lower bound as the producer controls the head index, + but the consumer may still be depleting the buffer on another CPU and + moving the tail index. + + To the consumer it will show an upper bound as the producer may be busy + depleting the space. + + [2] CIRC_CNT*() are intended to be used in the consumer. To the consumer they + will return a lower bound as the consumer controls the tail index, but the + producer may still be filling the buffer on another CPU and moving the + head index. + + To the producer it will show an upper bound as the consumer may be busy + emptying the buffer. + + [3] To a third party, the order in which the writes to the indices by the + producer and consumer become visible cannot be guaranteed as they are + independent and may be made on different CPUs - so the result in such a + situation will merely be a guess, and may even be negative. + + +=========================================== +USING MEMORY BARRIERS WITH CIRCULAR BUFFERS +=========================================== + +By using memory barriers in conjunction with circular buffers, you can avoid +the need to: + + (1) use a single lock to govern access to both ends of the buffer, thus + allowing the buffer to be filled and emptied at the same time; and + + (2) use atomic counter operations. + +There are two sides to this: the producer that fills the buffer, and the +consumer that empties it. Only one thing should be filling a buffer at any one +time, and only one thing should be emptying a buffer at any one time, but the +two sides can operate simultaneously. + + +THE PRODUCER +------------ + +The producer will look something like this: + + spin_lock(&producer_lock); + + unsigned long head = buffer->head; + unsigned long tail = ACCESS_ONCE(buffer->tail); + + if (CIRC_SPACE(head, tail, buffer->size) >= 1) { + /* insert one item into the buffer */ + struct item *item = buffer[head]; + + produce_item(item); + + smp_wmb(); /* commit the item before incrementing the head */ + + buffer->head = (head + 1) & (buffer->size - 1); + + /* wake_up() will make sure that the head is committed before + * waking anyone up */ + wake_up(consumer); + } + + spin_unlock(&producer_lock); + +This will instruct the CPU that the contents of the new item must be written +before the head index makes it available to the consumer and then instructs the +CPU that the revised head index must be written before the consumer is woken. + +Note that wake_up() doesn't have to be the exact mechanism used, but whatever +is used must guarantee a (write) memory barrier between the update of the head +index and the change of state of the consumer, if a change of state occurs. + + +THE CONSUMER +------------ + +The consumer will look something like this: + + spin_lock(&consumer_lock); + + unsigned long head = ACCESS_ONCE(buffer->head); + unsigned long tail = buffer->tail; + + if (CIRC_CNT(head, tail, buffer->size) >= 1) { + /* read index before reading contents at that index */ + smp_read_barrier_depends(); + + /* extract one item from the buffer */ + struct item *item = buffer[tail]; + + consume_item(item); + + smp_mb(); /* finish reading descriptor before incrementing tail */ + + buffer->tail = (tail + 1) & (buffer->size - 1); + } + + spin_unlock(&consumer_lock); + +This will instruct the CPU to make sure the index is up to date before reading +the new item, and then it shall make sure the CPU has finished reading the item +before it writes the new tail pointer, which will erase the item. + + +Note the use of ACCESS_ONCE() in both algorithms to read the opposition index. +This prevents the compiler from discarding and reloading its cached value - +which some compilers will do across smp_read_barrier_depends(). This isn't +strictly needed if you can be sure that the opposition index will _only_ be +used the once. + + +=============== +FURTHER READING +=============== + +See also Documentation/memory-barriers.txt for a description of Linux's memory +barrier facilities. diff --git a/Documentation/connector/cn_test.c b/Documentation/connector/cn_test.c index b07add3467f..7764594778d 100644 --- a/Documentation/connector/cn_test.c +++ b/Documentation/connector/cn_test.c @@ -25,6 +25,7 @@ #include <linux/module.h> #include <linux/moduleparam.h> #include <linux/skbuff.h> +#include <linux/slab.h> #include <linux/timer.h> #include <linux/connector.h> diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX index 3bae418c6ad..4303614b5ad 100644 --- a/Documentation/filesystems/00-INDEX +++ b/Documentation/filesystems/00-INDEX @@ -16,6 +16,8 @@ befs.txt - information about the BeOS filesystem for Linux. bfs.txt - info for the SCO UnixWare Boot Filesystem (BFS). +ceph.txt + - info for the Ceph Distributed File System cifs.txt - description of the CIFS filesystem. coda.txt diff --git a/Documentation/filesystems/9p.txt b/Documentation/filesystems/9p.txt index 57e0b80a527..c0236e753bc 100644 --- a/Documentation/filesystems/9p.txt +++ b/Documentation/filesystems/9p.txt @@ -37,6 +37,15 @@ For Plan 9 From User Space applications (http://swtch.com/plan9) mount -t 9p `namespace`/acme /mnt/9 -o trans=unix,uname=$USER +For server running on QEMU host with virtio transport: + + mount -t 9p -o trans=virtio <mount_tag> /mnt/9 + +where mount_tag is the tag associated by the server to each of the exported +mount points. Each 9P export is seen by the client as a virtio device with an +associated "mount_tag" property. Available mount tags can be +seen by reading /sys/bus/virtio/drivers/9pnet_virtio/virtio<n>/mount_tag files. + OPTIONS ======= @@ -47,7 +56,7 @@ OPTIONS fd - used passed file descriptors for connection (see rfdno and wfdno) virtio - connect to the next virtio channel available - (from lguest or KVM with trans_virtio module) + (from QEMU with trans_virtio module) rdma - connect to a specified RDMA channel uname=name user name to attempt mount as on the remote server. The @@ -85,7 +94,12 @@ OPTIONS port=n port to connect to on the remote server - noextend force legacy mode (no 9p2000.u semantics) + noextend force legacy mode (no 9p2000.u or 9p2000.L semantics) + + version=name Select 9P protocol version. Valid options are: + 9p2000 - Legacy mode (same as noextend) + 9p2000.u - Use 9P2000.u protocol + 9p2000.L - Use 9P2000.L protocol dfltuid attempt to mount as a particular uid diff --git a/Documentation/filesystems/ceph.txt b/Documentation/filesystems/ceph.txt index 6e03917316b..0660c9f5dee 100644 --- a/Documentation/filesystems/ceph.txt +++ b/Documentation/filesystems/ceph.txt @@ -8,7 +8,7 @@ Basic features include: * POSIX semantics * Seamless scaling from 1 to many thousands of nodes - * High availability and reliability. No single points of failure. + * High availability and reliability. No single point of failure. * N-way replication of data across storage nodes * Fast recovery from node failures * Automatic rebalancing of data on node addition/removal @@ -94,7 +94,7 @@ Mount Options wsize=X Specify the maximum write size in bytes. By default there is no - maximu. Ceph will normally size writes based on the file stripe + maximum. Ceph will normally size writes based on the file stripe size. rsize=X @@ -115,7 +115,7 @@ Mount Options number of entries in that directory. nocrc - Disable CRC32C calculation for data writes. If set, the OSD + Disable CRC32C calculation for data writes. If set, the storage node must rely on TCP's error correction to detect data corruption in the data payload. @@ -133,7 +133,8 @@ For more information on Ceph, see the home page at http://ceph.newdream.net/ The Linux kernel client source tree is available at - git://ceph.newdream.net/linux-ceph-client.git + git://ceph.newdream.net/git/ceph-client.git + git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client.git and the source for the full system is at - git://ceph.newdream.net/ceph.git + git://ceph.newdream.net/git/ceph.git diff --git a/Documentation/filesystems/tmpfs.txt b/Documentation/filesystems/tmpfs.txt index 3015da0c6b2..fe09a2cb185 100644 --- a/Documentation/filesystems/tmpfs.txt +++ b/Documentation/filesystems/tmpfs.txt @@ -82,11 +82,13 @@ tmpfs has a mount option to set the NUMA memory allocation policy for all files in that instance (if CONFIG_NUMA is enabled) - which can be adjusted on the fly via 'mount -o remount ...' -mpol=default prefers to allocate memory from the local node +mpol=default use the process allocation policy + (see set_mempolicy(2)) mpol=prefer:Node prefers to allocate memory from the given Node mpol=bind:NodeList allocates memory only from nodes in NodeList mpol=interleave prefers to allocate from each node in turn mpol=interleave:NodeList allocates from each node of NodeList in turn +mpol=local prefers to allocate memory from the local node NodeList format is a comma-separated list of decimal numbers and ranges, a range being two hyphen-separated decimal numbers, the smallest and @@ -134,3 +136,5 @@ Author: Christoph Rohland <cr@sap.com>, 1.12.01 Updated: Hugh Dickins, 4 June 2007 +Updated: + KOSAKI Motohiro, 16 Mar 2010 diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt index 7f5809eddee..631ad2f1b22 100644 --- a/Documentation/memory-barriers.txt +++ b/Documentation/memory-barriers.txt @@ -3,6 +3,7 @@ ============================ By: David Howells <dhowells@redhat.com> + Paul E. McKenney <paulmck@linux.vnet.ibm.com> Contents: @@ -60,6 +61,10 @@ Contents: - And then there's the Alpha. + (*) Example uses. + + - Circular buffers. + (*) References. @@ -2226,6 +2231,21 @@ The Alpha defines the Linux kernel's memory barrier model. See the subsection on "Cache Coherency" above. +============ +EXAMPLE USES +============ + +CIRCULAR BUFFERS +---------------- + +Memory barriers can be used to implement circular buffering without the need +of a lock to serialise the producer with the consumer. See: + + Documentation/circular-buffers.txt + +for details. + + ========== REFERENCES ========== diff --git a/Documentation/powerpc/dts-bindings/fsl/cpm_qe/qe.txt b/Documentation/powerpc/dts-bindings/fsl/cpm_qe/qe.txt index 6e37be1eeb2..4f8930263dd 100644 --- a/Documentation/powerpc/dts-bindings/fsl/cpm_qe/qe.txt +++ b/Documentation/powerpc/dts-bindings/fsl/cpm_qe/qe.txt @@ -21,6 +21,15 @@ Required properties: - fsl,qe-num-snums: define how many serial number(SNUM) the QE can use for the threads. +Optional properties: +- fsl,firmware-phandle: + Usage: required only if there is no fsl,qe-firmware child node + Value type: <phandle> + Definition: Points to a firmware node (see "QE Firmware Node" below) + that contains the firmware that should be uploaded for this QE. + The compatible property for the firmware node should say, + "fsl,qe-firmware". + Recommended properties - brg-frequency : the internal clock source frequency for baud-rate generators in Hz. @@ -59,3 +68,48 @@ Example: reg = <0 c000>; }; }; + +* QE Firmware Node + +This node defines a firmware binary that is embedded in the device tree, for +the purpose of passing the firmware from bootloader to the kernel, or from +the hypervisor to the guest. + +The firmware node itself contains the firmware binary contents, a compatible +property, and any firmware-specific properties. The node should be placed +inside a QE node that needs it. Doing so eliminates the need for a +fsl,firmware-phandle property. Other QE nodes that need the same firmware +should define an fsl,firmware-phandle property that points to the firmware node +in the first QE node. + +The fsl,firmware property can be specified in the DTS (possibly using incbin) +or can be inserted by the boot loader at boot time. + +Required properties: + - compatible + Usage: required + Value type: <string> + Definition: A standard property. Specify a string that indicates what + kind of firmware it is. For QE, this should be "fsl,qe-firmware". + + - fsl,firmware + Usage: required + Value type: <prop-encoded-array>, encoded as an array of bytes + Definition: A standard property. This property contains the firmware + binary "blob". + +Example: + qe1@e0080000 { + compatible = "fsl,qe"; + qe_firmware:qe-firmware { + compatible = "fsl,qe-firmware"; + fsl,firmware = [0x70 0xcd 0x00 0x00 0x01 0x46 0x45 ...]; + }; + ... + }; + + qe2@e0090000 { + compatible = "fsl,qe"; + fsl,firmware-phandle = <&qe_firmware>; + ... + }; diff --git a/Documentation/volatile-considered-harmful.txt b/Documentation/volatile-considered-harmful.txt index 991c26a6ef6..db0cb228d64 100644 --- a/Documentation/volatile-considered-harmful.txt +++ b/Documentation/volatile-considered-harmful.txt @@ -63,9 +63,9 @@ way to perform a busy wait is: cpu_relax(); The cpu_relax() call can lower CPU power consumption or yield to a -hyperthreaded twin processor; it also happens to serve as a memory barrier, -so, once again, volatile is unnecessary. Of course, busy-waiting is -generally an anti-social act to begin with. +hyperthreaded twin processor; it also happens to serve as a compiler +barrier, so, once again, volatile is unnecessary. Of course, busy- +waiting is generally an anti-social act to begin with. There are still a few rare situations where volatile makes sense in the kernel: |