debugging - What do the different columns in the "!heap -flt -s xxxx" windbg command represent -



debugging - What do the different columns in the "!heap -flt -s xxxx" windbg command represent -

i've been doing work on high memory issues, , i've been doing lot of heap analysis in windbg, , curious different columns mean in "!heap -flt -s xxxx" command.

i read what 'size' numbers mean in windbg !heap output?, , looked in "windows internals" book, still had bunch of questions. columns , questions below.

**heap_entry** - pointer point to? how different userptr? **size** - size mean? how different usersize? **prev** - appears negative offset previous heap entry. still not sure how it's used. **flags** - there documentation on these flags? **userptr** - user pointer? in cases i've seen it's 8 bytes higher heap_entry, don't know points to. **usersize** - appears size of actual allocation. **state** - tells state of heap entry (free, busy, etc....) example: heap_entry size prev flags userptr usersize - state 0015eeb0 0044 0000 [07] 0015eeb8 00204 - (busy)

heap_entry heaps store allocated blocks in contiguous segments of memory, each allocated block starts 8-bytes header followed actual allocated data. heap_entry column address of origin of header of allocated block.

size heap manager handles blocks in multiple of 8 bytes. column number of 8 bytes chunk allocated. in sample, 0044 means block takes 0x220 bytes (0x44*8).

prev multiply per 8 have negative offset in bytes previous heap block.

flags bitmask encodes next information

0x01 - heap_entry_busy 0x02 - heap_entry_extra_present 0x04 - heap_entry_fill_pattern 0x08 - heap_entry_virtual_alloc 0x10 - heap_entry_last_entry

userptr pointer returned application heapalloc (callbed malloc/new) function. since header 8 bytes long, heap_entry +8.

usersize size passed heapalloc function.

state decoding of flags column, telling if entry busy, freed, lastly of segment, …

be aware in windows 7/2008 r2, heaps default using front-end named lfh (low fragmented heap) uses default heap manager allocate chunks in dispatched user allocated data. these heaps, userptr , usersize not point real user data. output of !heap -s displays heaps lfh enabled.

debugging heap windbg

Comments

Post a Comment

Popular posts from this blog

iphone - Dismissing a UIAlertView -

iphone - Dismissing a UIAlertView - i set in app purchase app, , when user taps button, purchase started. basically, tap button, , depending on speed on net connection, waiting 10 seconds until new alert view comes asking if purchase product. user tap button multiple times since nil came up, , multiple purchase alert views come up. additionally, maybe seen user app bug. in end, problem. i want alert view come spinning wheel says "loading..." when users taps purchase button. problem is, how dismiss when new alert view comes asking user if want purchase product? if ([uialertview alloc] says: @"whatever apple's alert view says") { //dismiss "loading..." alert view here } i uncertainty work, input appreciated. thanks! you need have access alertview. can this. create alertview instance var in app delegate , when want show loading initialize instance var assign property , when want dismiss phone call [alertviewinstance d...
Read more

intellij idea - Update external libraries with intelij and java -

intellij idea - Update external libraries with intelij and java - simple plenty really. i'm using apache jars, i'll create changes jar's every often. these jars listed external libs in intelij (i.e classpath looking install dir of jar's). when create changes intelij doesn't seem know new implementation. have remove jar external library , re-ad it. does know have intelij picks changes automatically ? i've done clean , rebuild project had little effect. you can go preferences -> build, execution, deployment -> build tools -> maven -> importing , check box says import maven projects automatically . in mac, can command + shift + a , come in action reimport , click on reimport maven projects . intellij-idea
Read more

javascript - send data from a new window to previous window in php -

javascript - send data from a new window to previous window in php - i have image in main.php file : <img src="..\images\image.gif" class="cur" onclick="imgwin();"> when click on image below function has called : function imgwin() { imagewin=window.open("../pages/img.php","imagewin","toolbar=no,width=500,height=200,directories=no,menubar=no,scrollbars=yes"); } this function opens img.php in new window img.php file : <html> <head> <title>upload image</title> </head> <body> <form name="imgform" method="get" action="#"> address : <input type="file" name="imgurl" size="50"> description : <input type="text" name="description" size="50"> <input type="submit" value="sumbit...
Read more