aboutsummaryrefslogtreecommitdiffstats
path: root/Documentation
diff options
context:
space:
mode:
authorIngo Molnar <mingo@elte.hu>2008-06-16 05:20:37 -0400
committerIngo Molnar <mingo@elte.hu>2008-06-16 05:20:37 -0400
commit3557b18fcbe0e29706214f3c7cc680a7823605eb (patch)
tree2a70696b78a9e8b5ba38090901301931d395ecfb /Documentation
parent4226ab93d8ae3fd895abe45879fe34d489a98718 (diff)
parent066519068ad2fbe98c7f45552b1f592903a9c8c8 (diff)
Merge branch 'linus' into x86/ptemask
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/SubmittingPatches46
-rw-r--r--Documentation/cciss.txt5
-rw-r--r--Documentation/cpusets.txt9
-rw-r--r--Documentation/filesystems/ext4.txt12
-rw-r--r--Documentation/filesystems/sysfs-pci.txt1
-rw-r--r--Documentation/kernel-doc-nano-HOWTO.txt99
-rw-r--r--Documentation/kernel-docs.txt8
-rw-r--r--Documentation/kobject.txt2
-rw-r--r--Documentation/laptops/thinkpad-acpi.txt2
-rw-r--r--Documentation/lguest/lguest.c12
-rw-r--r--Documentation/networking/arcnet.txt2
-rw-r--r--Documentation/networking/bridge.txt2
-rw-r--r--Documentation/video4linux/CARDLIST.cx882
-rw-r--r--Documentation/video4linux/cx18.txt4
-rw-r--r--Documentation/vm/pagemap.txt77
15 files changed, 266 insertions, 17 deletions
diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index 9c93a03ea33b..118ca6e9404f 100644
--- a/Documentation/SubmittingPatches
+++ b/Documentation/SubmittingPatches
@@ -327,6 +327,52 @@ Some people also put extra tags at the end. They'll just be ignored for
327now, but you can do this to mark internal company procedures or just 327now, but you can do this to mark internal company procedures or just
328point out some special detail about the sign-off. 328point out some special detail about the sign-off.
329 329
330If you are a subsystem or branch maintainer, sometimes you need to slightly
331modify patches you receive in order to merge them, because the code is not
332exactly the same in your tree and the submitters'. If you stick strictly to
333rule (c), you should ask the submitter to rediff, but this is a totally
334counter-productive waste of time and energy. Rule (b) allows you to adjust
335the code, but then it is very impolite to change one submitter's code and
336make him endorse your bugs. To solve this problem, it is recommended that
337you add a line between the last Signed-off-by header and yours, indicating
338the nature of your changes. While there is nothing mandatory about this, it
339seems like prepending the description with your mail and/or name, all
340enclosed in square brackets, is noticeable enough to make it obvious that
341you are responsible for last-minute changes. Example :
342
343 Signed-off-by: Random J Developer <random@developer.example.org>
344 [lucky@maintainer.example.org: struct foo moved from foo.c to foo.h]
345 Signed-off-by: Lucky K Maintainer <lucky@maintainer.example.org>
346
347This practise is particularly helpful if you maintain a stable branch and
348want at the same time to credit the author, track changes, merge the fix,
349and protect the submitter from complaints. Note that under no circumstances
350can you change the author's identity (the From header), as it is the one
351which appears in the changelog.
352
353Special note to back-porters: It seems to be a common and useful practise
354to insert an indication of the origin of a patch at the top of the commit
355message (just after the subject line) to facilitate tracking. For instance,
356here's what we see in 2.6-stable :
357
358 Date: Tue May 13 19:10:30 2008 +0000
359
360 SCSI: libiscsi regression in 2.6.25: fix nop timer handling
361
362 commit 4cf1043593db6a337f10e006c23c69e5fc93e722 upstream
363
364And here's what appears in 2.4 :
365
366 Date: Tue May 13 22:12:27 2008 +0200
367
368 wireless, airo: waitbusy() won't delay
369
370 [backport of 2.6 commit b7acbdfbd1f277c1eb23f344f899cfa4cd0bf36a]
371
372Whatever the format, this information provides a valuable help to people
373tracking your trees, and to people trying to trouble-shoot bugs in your
374tree.
375
330 376
33113) When to use Acked-by: and Cc: 37713) When to use Acked-by: and Cc:
332 378
diff --git a/Documentation/cciss.txt b/Documentation/cciss.txt
index e65736c6b8bc..63e59b8847c5 100644
--- a/Documentation/cciss.txt
+++ b/Documentation/cciss.txt
@@ -21,6 +21,11 @@ This driver is known to work with the following cards:
21 * SA E200 21 * SA E200
22 * SA E200i 22 * SA E200i
23 * SA E500 23 * SA E500
24 * SA P212
25 * SA P410
26 * SA P410i
27 * SA P411
28 * SA P812
24 29
25Detecting drive failures: 30Detecting drive failures:
26------------------------- 31-------------------------
diff --git a/Documentation/cpusets.txt b/Documentation/cpusets.txt
index fb7b361e6eea..d803c5c68ab5 100644
--- a/Documentation/cpusets.txt
+++ b/Documentation/cpusets.txt
@@ -199,7 +199,7 @@ using the sched_setaffinity, mbind and set_mempolicy system calls.
199The following rules apply to each cpuset: 199The following rules apply to each cpuset:
200 200
201 - Its CPUs and Memory Nodes must be a subset of its parents. 201 - Its CPUs and Memory Nodes must be a subset of its parents.
202 - It can only be marked exclusive if its parent is. 202 - It can't be marked exclusive unless its parent is.
203 - If its cpu or memory is exclusive, they may not overlap any sibling. 203 - If its cpu or memory is exclusive, they may not overlap any sibling.
204 204
205These rules, and the natural hierarchy of cpusets, enable efficient 205These rules, and the natural hierarchy of cpusets, enable efficient
@@ -345,7 +345,7 @@ is modified to perform an inline check for this PF_SPREAD_PAGE task
345flag, and if set, a call to a new routine cpuset_mem_spread_node() 345flag, and if set, a call to a new routine cpuset_mem_spread_node()
346returns the node to prefer for the allocation. 346returns the node to prefer for the allocation.
347 347
348Similarly, setting 'memory_spread_cache' turns on the flag 348Similarly, setting 'memory_spread_slab' turns on the flag
349PF_SPREAD_SLAB, and appropriately marked slab caches will allocate 349PF_SPREAD_SLAB, and appropriately marked slab caches will allocate
350pages from the node returned by cpuset_mem_spread_node(). 350pages from the node returned by cpuset_mem_spread_node().
351 351
@@ -709,7 +709,10 @@ Now you want to do something with this cpuset.
709 709
710In this directory you can find several files: 710In this directory you can find several files:
711# ls 711# ls
712cpus cpu_exclusive mems mem_exclusive mem_hardwall tasks 712cpu_exclusive memory_migrate mems tasks
713cpus memory_pressure notify_on_release
714mem_exclusive memory_spread_page sched_load_balance
715mem_hardwall memory_spread_slab sched_relax_domain_level
713 716
714Reading them will give you information about the state of this cpuset: 717Reading them will give you information about the state of this cpuset:
715the CPUs and Memory Nodes it can use, the processes that are using 718the CPUs and Memory Nodes it can use, the processes that are using
diff --git a/Documentation/filesystems/ext4.txt b/Documentation/filesystems/ext4.txt
index 560f88dc7090..0c5086db8352 100644
--- a/Documentation/filesystems/ext4.txt
+++ b/Documentation/filesystems/ext4.txt
@@ -139,8 +139,16 @@ commit=nrsec (*) Ext4 can be told to sync all its data and metadata
139 Setting it to very large values will improve 139 Setting it to very large values will improve
140 performance. 140 performance.
141 141
142barrier=1 This enables/disables barriers. barrier=0 disables 142barrier=<0|1(*)> This enables/disables the use of write barriers in
143 it, barrier=1 enables it. 143 the jbd code. barrier=0 disables, barrier=1 enables.
144 This also requires an IO stack which can support
145 barriers, and if jbd gets an error on a barrier
146 write, it will disable again with a warning.
147 Write barriers enforce proper on-disk ordering
148 of journal commits, making volatile disk write caches
149 safe to use, at some performance penalty. If
150 your disks are battery-backed in one way or another,
151 disabling barriers may safely improve performance.
144 152
145orlov (*) This enables the new Orlov block allocator. It is 153orlov (*) This enables the new Orlov block allocator. It is
146 enabled by default. 154 enabled by default.
diff --git a/Documentation/filesystems/sysfs-pci.txt b/Documentation/filesystems/sysfs-pci.txt
index 5daa2aaec2c5..68ef48839c04 100644
--- a/Documentation/filesystems/sysfs-pci.txt
+++ b/Documentation/filesystems/sysfs-pci.txt
@@ -36,6 +36,7 @@ files, each with their own function.
36 local_cpus nearby CPU mask (cpumask, ro) 36 local_cpus nearby CPU mask (cpumask, ro)
37 resource PCI resource host addresses (ascii, ro) 37 resource PCI resource host addresses (ascii, ro)
38 resource0..N PCI resource N, if present (binary, mmap) 38 resource0..N PCI resource N, if present (binary, mmap)
39 resource0_wc..N_wc PCI WC map resource N, if prefetchable (binary, mmap)
39 rom PCI ROM resource, if present (binary, ro) 40 rom PCI ROM resource, if present (binary, ro)
40 subsystem_device PCI subsystem device (ascii, ro) 41 subsystem_device PCI subsystem device (ascii, ro)
41 subsystem_vendor PCI subsystem vendor (ascii, ro) 42 subsystem_vendor PCI subsystem vendor (ascii, ro)
diff --git a/Documentation/kernel-doc-nano-HOWTO.txt b/Documentation/kernel-doc-nano-HOWTO.txt
index 2075c0658bf5..0bd32748a467 100644
--- a/Documentation/kernel-doc-nano-HOWTO.txt
+++ b/Documentation/kernel-doc-nano-HOWTO.txt
@@ -1,6 +1,105 @@
1kernel-doc nano-HOWTO 1kernel-doc nano-HOWTO
2===================== 2=====================
3 3
4How to format kernel-doc comments
5---------------------------------
6
7In order to provide embedded, 'C' friendly, easy to maintain,
8but consistent and extractable documentation of the functions and
9data structures in the Linux kernel, the Linux kernel has adopted
10a consistent style for documenting functions and their parameters,
11and structures and their members.
12
13The format for this documentation is called the kernel-doc format.
14It is documented in this Documentation/kernel-doc-nano-HOWTO.txt file.
15
16This style embeds the documentation within the source files, using
17a few simple conventions. The scripts/kernel-doc perl script, some
18SGML templates in Documentation/DocBook, and other tools understand
19these conventions, and are used to extract this embedded documentation
20into various documents.
21
22In order to provide good documentation of kernel functions and data
23structures, please use the following conventions to format your
24kernel-doc comments in Linux kernel source.
25
26We definitely need kernel-doc formatted documentation for functions
27that are exported to loadable modules using EXPORT_SYMBOL.
28
29We also look to provide kernel-doc formatted documentation for
30functions externally visible to other kernel files (not marked
31"static").
32
33We also recommend providing kernel-doc formatted documentation
34for private (file "static") routines, for consistency of kernel
35source code layout. But this is lower priority and at the
36discretion of the MAINTAINER of that kernel source file.
37
38Data structures visible in kernel include files should also be
39documented using kernel-doc formatted comments.
40
41The opening comment mark "/**" is reserved for kernel-doc comments.
42Only comments so marked will be considered by the kernel-doc scripts,
43and any comment so marked must be in kernel-doc format. Do not use
44"/**" to be begin a comment block unless the comment block contains
45kernel-doc formatted comments. The closing comment marker for
46kernel-doc comments can be either "*/" or "**/".
47
48Kernel-doc comments should be placed just before the function
49or data structure being described.
50
51Example kernel-doc function comment:
52
53/**
54 * foobar() - short function description of foobar
55 * @arg1: Describe the first argument to foobar.
56 * @arg2: Describe the second argument to foobar.
57 * One can provide multiple line descriptions
58 * for arguments.
59 *
60 * A longer description, with more discussion of the function foobar()
61 * that might be useful to those using or modifying it. Begins with
62 * empty comment line, and may include additional embedded empty
63 * comment lines.
64 *
65 * The longer description can have multiple paragraphs.
66 **/
67
68The first line, with the short description, must be on a single line.
69
70The @argument descriptions must begin on the very next line following
71this opening short function description line, with no intervening
72empty comment lines.
73
74Example kernel-doc data structure comment.
75
76/**
77 * struct blah - the basic blah structure
78 * @mem1: describe the first member of struct blah
79 * @mem2: describe the second member of struct blah,
80 * perhaps with more lines and words.
81 *
82 * Longer description of this structure.
83 **/
84
85The kernel-doc function comments describe each parameter to the
86function, in order, with the @name lines.
87
88The kernel-doc data structure comments describe each structure member
89in the data structure, with the @name lines.
90
91The longer description formatting is "reflowed", losing your line
92breaks. So presenting carefully formatted lists within these
93descriptions won't work so well; derived documentation will lose
94the formatting.
95
96See the section below "How to add extractable documentation to your
97source files" for more details and notes on how to format kernel-doc
98comments.
99
100Components of the kernel-doc system
101-----------------------------------
102
4Many places in the source tree have extractable documentation in the 103Many places in the source tree have extractable documentation in the
5form of block comments above functions. The components of this system 104form of block comments above functions. The components of this system
6are: 105are:
diff --git a/Documentation/kernel-docs.txt b/Documentation/kernel-docs.txt
index 5a4ef48224ae..28cdc2af2131 100644
--- a/Documentation/kernel-docs.txt
+++ b/Documentation/kernel-docs.txt
@@ -715,14 +715,14 @@
715 715
716 * Name: "Gary's Encyclopedia - The Linux Kernel" 716 * Name: "Gary's Encyclopedia - The Linux Kernel"
717 Author: Gary (I suppose...). 717 Author: Gary (I suppose...).
718 URL: http://www.lisoleg.net/cgi-bin/lisoleg.pl?view=kernel.htm 718 URL: http://slencyclopedia.berlios.de/index.html
719 Keywords: links, not found here?. 719 Keywords: linux, community, everything!
720 Description: Gary's Encyclopedia exists to allow the rapid finding 720 Description: Gary's Encyclopedia exists to allow the rapid finding
721 of documentation and other information of interest to GNU/Linux 721 of documentation and other information of interest to GNU/Linux
722 users. It has about 4000 links to external pages in 150 major 722 users. It has about 4000 links to external pages in 150 major
723 categories. This link is for kernel-specific links, documents, 723 categories. This link is for kernel-specific links, documents,
724 sites... Look there if you could not find here what you were 724 sites... This list is now hosted by developer.Berlios.de,
725 looking for. 725 but seems not to have been updated since sometime in 1999.
726 726
727 * Name: "The home page of Linux-MM" 727 * Name: "The home page of Linux-MM"
728 Author: The Linux-MM team. 728 Author: The Linux-MM team.
diff --git a/Documentation/kobject.txt b/Documentation/kobject.txt
index bf3256e04027..51a8021ee532 100644
--- a/Documentation/kobject.txt
+++ b/Documentation/kobject.txt
@@ -305,7 +305,7 @@ should not be manipulated by any other user.
305 305
306A kset keeps its children in a standard kernel linked list. Kobjects point 306A kset keeps its children in a standard kernel linked list. Kobjects point
307back to their containing kset via their kset field. In almost all cases, 307back to their containing kset via their kset field. In almost all cases,
308the kobjects belonging to a ket have that kset (or, strictly, its embedded 308the kobjects belonging to a kset have that kset (or, strictly, its embedded
309kobject) in their parent. 309kobject) in their parent.
310 310
311As a kset contains a kobject within it, it should always be dynamically 311As a kset contains a kobject within it, it should always be dynamically
diff --git a/Documentation/laptops/thinkpad-acpi.txt b/Documentation/laptops/thinkpad-acpi.txt
index 01c6c3d8a7e3..64b3f146e4b0 100644
--- a/Documentation/laptops/thinkpad-acpi.txt
+++ b/Documentation/laptops/thinkpad-acpi.txt
@@ -503,7 +503,7 @@ generate input device EV_KEY events.
503In addition to the EV_KEY events, thinkpad-acpi may also issue EV_SW 503In addition to the EV_KEY events, thinkpad-acpi may also issue EV_SW
504events for switches: 504events for switches:
505 505
506SW_RADIO T60 and later hardare rfkill rocker switch 506SW_RFKILL_ALL T60 and later hardare rfkill rocker switch
507SW_TABLET_MODE Tablet ThinkPads HKEY events 0x5009 and 0x500A 507SW_TABLET_MODE Tablet ThinkPads HKEY events 0x5009 and 0x500A
508 508
509Non hot-key ACPI HKEY event map: 509Non hot-key ACPI HKEY event map:
diff --git a/Documentation/lguest/lguest.c b/Documentation/lguest/lguest.c
index 3be8ab2a886a..82fafe0429fe 100644
--- a/Documentation/lguest/lguest.c
+++ b/Documentation/lguest/lguest.c
@@ -157,6 +157,9 @@ struct virtqueue
157 157
158 /* The routine to call when the Guest pings us. */ 158 /* The routine to call when the Guest pings us. */
159 void (*handle_output)(int fd, struct virtqueue *me); 159 void (*handle_output)(int fd, struct virtqueue *me);
160
161 /* Outstanding buffers */
162 unsigned int inflight;
160}; 163};
161 164
162/* Remember the arguments to the program so we can "reboot" */ 165/* Remember the arguments to the program so we can "reboot" */
@@ -702,6 +705,7 @@ static unsigned get_vq_desc(struct virtqueue *vq,
702 errx(1, "Looped descriptor"); 705 errx(1, "Looped descriptor");
703 } while ((i = next_desc(vq, i)) != vq->vring.num); 706 } while ((i = next_desc(vq, i)) != vq->vring.num);
704 707
708 vq->inflight++;
705 return head; 709 return head;
706} 710}
707 711
@@ -719,6 +723,7 @@ static void add_used(struct virtqueue *vq, unsigned int head, int len)
719 /* Make sure buffer is written before we update index. */ 723 /* Make sure buffer is written before we update index. */
720 wmb(); 724 wmb();
721 vq->vring.used->idx++; 725 vq->vring.used->idx++;
726 vq->inflight--;
722} 727}
723 728
724/* This actually sends the interrupt for this virtqueue */ 729/* This actually sends the interrupt for this virtqueue */
@@ -726,8 +731,9 @@ static void trigger_irq(int fd, struct virtqueue *vq)
726{ 731{
727 unsigned long buf[] = { LHREQ_IRQ, vq->config.irq }; 732 unsigned long buf[] = { LHREQ_IRQ, vq->config.irq };
728 733
729 /* If they don't want an interrupt, don't send one. */ 734 /* If they don't want an interrupt, don't send one, unless empty. */
730 if (vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT) 735 if ((vq->vring.avail->flags & VRING_AVAIL_F_NO_INTERRUPT)
736 && vq->inflight)
731 return; 737 return;
732 738
733 /* Send the Guest an interrupt tell them we used something up. */ 739 /* Send the Guest an interrupt tell them we used something up. */
@@ -1107,6 +1113,7 @@ static void add_virtqueue(struct device *dev, unsigned int num_descs,
1107 vq->next = NULL; 1113 vq->next = NULL;
1108 vq->last_avail_idx = 0; 1114 vq->last_avail_idx = 0;
1109 vq->dev = dev; 1115 vq->dev = dev;
1116 vq->inflight = 0;
1110 1117
1111 /* Initialize the configuration. */ 1118 /* Initialize the configuration. */
1112 vq->config.num = num_descs; 1119 vq->config.num = num_descs;
@@ -1368,6 +1375,7 @@ static void setup_tun_net(const char *arg)
1368 1375
1369 /* Tell Guest what MAC address to use. */ 1376 /* Tell Guest what MAC address to use. */
1370 add_feature(dev, VIRTIO_NET_F_MAC); 1377 add_feature(dev, VIRTIO_NET_F_MAC);
1378 add_feature(dev, VIRTIO_F_NOTIFY_ON_EMPTY);
1371 set_config(dev, sizeof(conf), &conf); 1379 set_config(dev, sizeof(conf), &conf);
1372 1380
1373 /* We don't need the socket any more; setup is done. */ 1381 /* We don't need the socket any more; setup is done. */
diff --git a/Documentation/networking/arcnet.txt b/Documentation/networking/arcnet.txt
index 770fc41a78e8..796012540386 100644
--- a/Documentation/networking/arcnet.txt
+++ b/Documentation/networking/arcnet.txt
@@ -46,7 +46,7 @@ These are the ARCnet drivers for Linux.
46 46
47 47
48This new release (2.91) has been put together by David Woodhouse 48This new release (2.91) has been put together by David Woodhouse
49<dwmw2@cam.ac.uk>, in an attempt to tidy up the driver after adding support 49<dwmw2@infradead.org>, in an attempt to tidy up the driver after adding support
50for yet another chipset. Now the generic support has been separated from the 50for yet another chipset. Now the generic support has been separated from the
51individual chipset drivers, and the source files aren't quite so packed with 51individual chipset drivers, and the source files aren't quite so packed with
52#ifdefs! I've changed this file a bit, but kept it in the first person from 52#ifdefs! I've changed this file a bit, but kept it in the first person from
diff --git a/Documentation/networking/bridge.txt b/Documentation/networking/bridge.txt
index bdae2db4119c..bec69a8a1697 100644
--- a/Documentation/networking/bridge.txt
+++ b/Documentation/networking/bridge.txt
@@ -1,6 +1,6 @@
1In order to use the Ethernet bridging functionality, you'll need the 1In order to use the Ethernet bridging functionality, you'll need the
2userspace tools. These programs and documentation are available 2userspace tools. These programs and documentation are available
3at http://bridge.sourceforge.net. The download page is 3at http://www.linux-foundation.org/en/Net:Bridge. The download page is
4http://prdownloads.sourceforge.net/bridge. 4http://prdownloads.sourceforge.net/bridge.
5 5
6If you still have questions, don't hesitate to post to the mailing list 6If you still have questions, don't hesitate to post to the mailing list
diff --git a/Documentation/video4linux/CARDLIST.cx88 b/Documentation/video4linux/CARDLIST.cx88
index 543957346469..7cf5685d3645 100644
--- a/Documentation/video4linux/CARDLIST.cx88
+++ b/Documentation/video4linux/CARDLIST.cx88
@@ -60,7 +60,7 @@
60 59 -> DViCO FusionHDTV 5 PCI nano [18ac:d530] 60 59 -> DViCO FusionHDTV 5 PCI nano [18ac:d530]
61 60 -> Pinnacle Hybrid PCTV [12ab:1788] 61 60 -> Pinnacle Hybrid PCTV [12ab:1788]
62 61 -> Winfast TV2000 XP Global [107d:6f18] 62 61 -> Winfast TV2000 XP Global [107d:6f18]
63 62 -> PowerColor Real Angel 330 [14f1:ea3d] 63 62 -> PowerColor RA330 [14f1:ea3d]
64 63 -> Geniatech X8000-MT DVBT [14f1:8852] 64 63 -> Geniatech X8000-MT DVBT [14f1:8852]
65 64 -> DViCO FusionHDTV DVB-T PRO [18ac:db30] 65 64 -> DViCO FusionHDTV DVB-T PRO [18ac:db30]
66 65 -> DViCO FusionHDTV 7 Gold [18ac:d610] 66 65 -> DViCO FusionHDTV 7 Gold [18ac:d610]
diff --git a/Documentation/video4linux/cx18.txt b/Documentation/video4linux/cx18.txt
index 077d56ec3f3d..6842c262890f 100644
--- a/Documentation/video4linux/cx18.txt
+++ b/Documentation/video4linux/cx18.txt
@@ -1,7 +1,9 @@
1Some notes regarding the cx18 driver for the Conexant CX23418 MPEG 1Some notes regarding the cx18 driver for the Conexant CX23418 MPEG
2encoder chip: 2encoder chip:
3 3
41) The only hardware currently supported is the Hauppauge HVR-1600. 41) The only hardware currently supported is the Hauppauge HVR-1600
5 card and the Compro VideoMate H900 (note that this card only
6 supports analog input, it has no digital tuner!).
5 7
62) Some people have problems getting the i2c bus to work. Cause unknown. 82) Some people have problems getting the i2c bus to work. Cause unknown.
7 The symptom is that the eeprom cannot be read and the card is 9 The symptom is that the eeprom cannot be read and the card is
diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt
new file mode 100644
index 000000000000..ce72c0fe6177
--- /dev/null
+++ b/Documentation/vm/pagemap.txt
@@ -0,0 +1,77 @@
1pagemap, from the userspace perspective
2---------------------------------------
3
4pagemap is a new (as of 2.6.25) set of interfaces in the kernel that allow
5userspace programs to examine the page tables and related information by
6reading files in /proc.
7
8There are three components to pagemap:
9
10 * /proc/pid/pagemap. This file lets a userspace process find out which
11 physical frame each virtual page is mapped to. It contains one 64-bit
12 value for each virtual page, containing the following data (from
13 fs/proc/task_mmu.c, above pagemap_read):
14
15 * Bits 0-55 page frame number (PFN) if present
16 * Bits 0-4 swap type if swapped
17 * Bits 5-55 swap offset if swapped
18 * Bits 55-60 page shift (page size = 1<<page shift)
19 * Bit 61 reserved for future use
20 * Bit 62 page swapped
21 * Bit 63 page present
22
23 If the page is not present but in swap, then the PFN contains an
24 encoding of the swap file number and the page's offset into the
25 swap. Unmapped pages return a null PFN. This allows determining
26 precisely which pages are mapped (or in swap) and comparing mapped
27 pages between processes.
28
29 Efficient users of this interface will use /proc/pid/maps to
30 determine which areas of memory are actually mapped and llseek to
31 skip over unmapped regions.
32
33 * /proc/kpagecount. This file contains a 64-bit count of the number of
34 times each page is mapped, indexed by PFN.
35
36 * /proc/kpageflags. This file contains a 64-bit set of flags for each
37 page, indexed by PFN.
38
39 The flags are (from fs/proc/proc_misc, above kpageflags_read):
40
41 0. LOCKED
42 1. ERROR
43 2. REFERENCED
44 3. UPTODATE
45 4. DIRTY
46 5. LRU
47 6. ACTIVE
48 7. SLAB
49 8. WRITEBACK
50 9. RECLAIM
51 10. BUDDY
52
53Using pagemap to do something useful:
54
55The general procedure for using pagemap to find out about a process' memory
56usage goes like this:
57
58 1. Read /proc/pid/maps to determine which parts of the memory space are
59 mapped to what.
60 2. Select the maps you are interested in -- all of them, or a particular
61 library, or the stack or the heap, etc.
62 3. Open /proc/pid/pagemap and seek to the pages you would like to examine.
63 4. Read a u64 for each page from pagemap.
64 5. Open /proc/kpagecount and/or /proc/kpageflags. For each PFN you just
65 read, seek to that entry in the file, and read the data you want.
66
67For example, to find the "unique set size" (USS), which is the amount of
68memory that a process is using that is not shared with any other process,
69you can go through every map in the process, find the PFNs, look those up
70in kpagecount, and tally up the number of pages that are only referenced
71once.
72
73Other notes:
74
75Reading from any of the files will return -EINVAL if you are not starting
76the read on an 8-byte boundary (e.g., if you seeked an odd number of bytes
77into the file), or if the size of the read is not a multiple of 8 bytes.