<html><body> I too have been trying to reproduce the existence of Private_Clean memory segments in smaps via a simple test case with jemalloc and was unable to on my laptop, a 2 core machine running a 3.8.0-23 kernel . I then moved my test to our production box: 96GB memory, 24 hardware threads and 2.6 kernel (detailed information below), and within a few minutes of execution, with a few minor adjustments, I was able duplicate the results, smaps showing the jemalloc segment with Private_Clean memory usage, of our larger test. Note that I'm using the same jemalloc library whose information Kurtis posted earlier (96 arenas etc...). Thank you, Tom --------------- DETAILS Smaps memory segment 7f1f75c00000-7f35bce00000 rw-p 00000000 00:00 0 Size: 93440000 kB Rss: 63177024 kB Pss: 63177024 kB Shared_Clean: 0 kB Shared_Dirty: 0 kB Private_Clean: 614992 kB Private_Dirty: 62562032 kB Referenced: 62562212 kB Swap: 0 kB KernelPageSize: 4 kB MMUPageSize: 4 kB Production Box Info: # uname -a Linux 9.42.94.12 2.6.32-131.21.1.89.br5_0.x86_64 #1 SMP Tue Mar 19 15:05:57 CDT 2013 x86_64 GNU/Linux Tail of CPU Info processor : 23 vendor_id : GenuineIntel cpu family : 6 model : 44 model name : Intel(R) Xeon(R) CPU X5670 @ 2.93GHz stepping : 2 cpu MHz : 2933.304 cache size : 12288 KB physical id : 1 siblings : 12 core id : 10 cpu cores : 6 apicid : 53 initial apicid : 53 fpu : yes fpu_exception : yes cpuid level : 11 wp : yes flags : fpu vme de pse tsc msr pae mce cx8 apic mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe syscall nx pdpe1gb rdtscp lm constant_tsc arch_perfmon pebs bts rep_good xtopology nonstop_tsc aperfmperf pni pclmulqdq dtes64 monitor ds_cpl vmx smx est tm2 ssse3 cx16 xtpr pdcm dca sse4_1 sse4_2 popcnt aes lahf_lm ida arat tpr_shadow vnmi flexpriority ept vpid bogomips : 5867.23 clflush size : 64 cache_alignment : 64 address sizes : 40 bits physical, 48 bits virtual power management: (See attached file: stressTest.c)</body></html>