<html> <head> <link rel=stylesheet href="style.css" type="text/css"> <title>collectl - Memory Fragmentation</title> </head> <body> <center><h1>Memory Fragmentation</h1></center> <p> <h3>Introduction</h3> Version 3.2.1 of collectl introduces support for <i>/proc/buddyinfo</i>, which shows the distribution of memory fragments where the size of each fragment is a power of 2 pages. The memory is categorized by node, depending on the system architecture and then subcategorized by the type of memory, referred as a zone. For example, the <i>/proc/buddyinfo</i> might look like: <div class=terminal><pre> Node 0, zone DMA 5 5 3 4 2 4 3 1 0 0 0 Node 0, zone DMA32 79 61 4 12 0 0 0 2 0 1 0 Node 1, zone DMA32 134 57 27 60 0 0 1 1 0 1 0 Node 2, zone Normal 865 357 37 1 6 0 2 1 0 1 0 Node 3, zone Normal 651 47 19 10 1 1 1 1 0 1 0 </pre></div> Running collectl with <i>-sb --verbose</i> would produce a single line of output that shows the totals of each column. For example, taking 1 second samples with timestamps included: <div class=terminal><pre> collectl -sb --verbose -oT # MEMORY FRAGMENTATION SUMMARY (4K pages) # 1 2 4 8 16 32 64 128 256 512 1024 16:11:26 1296 483 157 85 9 5 7 6 0 4 0 16:11:27 1354 485 163 87 9 5 7 6 0 4 0 16:11:28 1395 480 165 89 9 5 7 6 0 4 0 </pre></div> And in detail mode we see one line per entry, again with timestamps: <div class=terminal-wide14><pre> collectl -sB -oT # MEMORY FRAGMENTATION (4K pages) # Node Zone 1 2 4 8 16 32 64 128 256 512 1024 16:13:33 0 DMA 5 5 3 4 2 4 3 1 0 0 0 16:13:33 0 DMA32 175 97 3 12 0 0 0 2 0 1 0 16:13:33 1 DMA32 933 389 60 68 0 0 1 1 0 1 0 16:13:33 2 Normal 0 1 8 1 6 0 2 1 0 1 0 16:13:33 3 Normal 1 2 57 10 1 1 1 1 0 1 0 </pre></div> Where things get interesting is in <i>brief</i> mode. The challege here is to show the maximum amount of information in the least amount of space, thus allowing you to look at other information on the same line as well. To better understand the methodology chosen for this, think in terms of <i>base 36</i>. However, instead of mapping each character to a number from 0 to 35, we're going to do something very different. Since we're mainly interested in seeing what's happening as the numbers of fragments shrink: <ul> <li>map the 0 through 9 to the characters 0 through 9</li> <li>map the numbers 10-99 to the characters <i>a</i> through <i>i</i> by dividing these values by 10</li> <li>fragments in the range of 100-999 will be divided by 100 and mapped to the letters <i>j</i> through r</i></li> <li>this only leaves us with the 8 letters <i>s</i> through <i>z</i> and being the coarsest will be mapped to powers of 10 by essentially dividing the value by 1000 and taking the log10() of it</li> </ul> This results in a display like the following: <div class=terminal><pre> collectl -sb -oT # <---Memory--> #Time Fragments 16:24:13 qmji9576040 16:24:14 rmji9576040 16:24:15 smji9576040 16:24:16 smji9576040 16:24:17 rmji9576040 </pre></div> As a final example of what this looks like when combined with other data, remembering you can choose virtually any combination of subsystem for your display both in collection and playback modes: <div class=terminal-wide14><pre> collectl -sbcmn -oT # <--------CPU--------><------------------Memory-----------------><----------Network----------> #Time cpu sys inter ctxsw Free Buff Cach Inac Slab Map Fragments KBIn PktIn KBOut PktOut 16:44:46 0 0 1029 146 23M 178M 6G 5G 461M 234M lljj9576040 2 8 0 2 16:44:47 0 0 1020 136 24M 178M 6G 5G 461M 234M nljj9576040 2 8 1 2 16:44:48 1 0 1062 371 22M 178M 6G 5G 461M 235M kljj9576040 3 31 2 27 16:44:49 0 0 1009 146 22M 178M 6G 5G 461M 235M kljj9576040 14 13 0 2 </pre></div> <table width=100%><tr><td align=right><i>updated Feb 12, 2009</i></td></tr></colgroup></table> </body> </html>
