diff options
Diffstat (limited to 'Documentation/vm')
| -rw-r--r-- | Documentation/vm/pagemap.txt | 77 | ||||
| -rw-r--r-- | Documentation/vm/slabinfo.c | 4 | ||||
| -rw-r--r-- | Documentation/vm/slub.txt | 2 |
3 files changed, 80 insertions, 3 deletions
diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt new file mode 100644 index 00000000000..ce72c0fe617 --- /dev/null +++ b/Documentation/vm/pagemap.txt @@ -0,0 +1,77 @@ +pagemap, from the userspace perspective +--------------------------------------- + +pagemap is a new (as of 2.6.25) set of interfaces in the kernel that allow +userspace programs to examine the page tables and related information by +reading files in /proc. + +There are three components to pagemap: + + * /proc/pid/pagemap. This file lets a userspace process find out which + physical frame each virtual page is mapped to. It contains one 64-bit + value for each virtual page, containing the following data (from + fs/proc/task_mmu.c, above pagemap_read): + + * Bits 0-55 page frame number (PFN) if present + * Bits 0-4 swap type if swapped + * Bits 5-55 swap offset if swapped + * Bits 55-60 page shift (page size = 1<<page shift) + * Bit 61 reserved for future use + * Bit 62 page swapped + * Bit 63 page present + + If the page is not present but in swap, then the PFN contains an + encoding of the swap file number and the page's offset into the + swap. Unmapped pages return a null PFN. This allows determining + precisely which pages are mapped (or in swap) and comparing mapped + pages between processes. + + Efficient users of this interface will use /proc/pid/maps to + determine which areas of memory are actually mapped and llseek to + skip over unmapped regions. + + * /proc/kpagecount. This file contains a 64-bit count of the number of + times each page is mapped, indexed by PFN. + + * /proc/kpageflags. This file contains a 64-bit set of flags for each + page, indexed by PFN. + + The flags are (from fs/proc/proc_misc, above kpageflags_read): + + 0. LOCKED + 1. ERROR + 2. REFERENCED + 3. UPTODATE + 4. DIRTY + 5. LRU + 6. ACTIVE + 7. SLAB + 8. WRITEBACK + 9. RECLAIM + 10. BUDDY + +Using pagemap to do something useful: + +The general procedure for using pagemap to find out about a process' memory +usage goes like this: + + 1. Read /proc/pid/maps to determine which parts of the memory space are + mapped to what. + 2. Select the maps you are interested in -- all of them, or a particular + library, or the stack or the heap, etc. + 3. Open /proc/pid/pagemap and seek to the pages you would like to examine. + 4. Read a u64 for each page from pagemap. + 5. Open /proc/kpagecount and/or /proc/kpageflags. For each PFN you just + read, seek to that entry in the file, and read the data you want. + +For example, to find the "unique set size" (USS), which is the amount of +memory that a process is using that is not shared with any other process, +you can go through every map in the process, find the PFNs, look those up +in kpagecount, and tally up the number of pages that are only referenced +once. + +Other notes: + +Reading from any of the files will return -EINVAL if you are not starting +the read on an 8-byte boundary (e.g., if you seeked an odd number of bytes +into the file), or if the size of the read is not a multiple of 8 bytes. diff --git a/Documentation/vm/slabinfo.c b/Documentation/vm/slabinfo.c index e4230ed16ee..df3227605d5 100644 --- a/Documentation/vm/slabinfo.c +++ b/Documentation/vm/slabinfo.c @@ -1,7 +1,7 @@ /* * Slabinfo: Tool to get reports about slabs * - * (C) 2007 sgi, Christoph Lameter <clameter@sgi.com> + * (C) 2007 sgi, Christoph Lameter * * Compile by: * @@ -99,7 +99,7 @@ void fatal(const char *x, ...) void usage(void) { - printf("slabinfo 5/7/2007. (c) 2007 sgi. clameter@sgi.com\n\n" + printf("slabinfo 5/7/2007. (c) 2007 sgi.\n\n" "slabinfo [-ahnpvtsz] [-d debugopts] [slab-regexp]\n" "-a|--aliases Show aliases\n" "-A|--activity Most active slabs first\n" diff --git a/Documentation/vm/slub.txt b/Documentation/vm/slub.txt index 7c13f22a0c9..bb1f5c6e28b 100644 --- a/Documentation/vm/slub.txt +++ b/Documentation/vm/slub.txt @@ -266,4 +266,4 @@ of other objects. slub_debug=FZ,dentry -Christoph Lameter, <clameter@sgi.com>, May 30, 2007 +Christoph Lameter, May 30, 2007 |