Solaris memory allocation
留个图。
这是Solaris 8+的内存分配图
Cache list + Free list = vmstat.free
reclaim = vmstat.re
Mapped file + Segmap File Cache = kstat -k::memstat中的page cache
而这个Segmap File Cache的大小在Solaris/SPARC有个限制,由/etc/system参数segmap_percent决定,默认是12。就是说segmap file cache的最大值可以为12%的物理内存大小. 也就说说 segmap file cache是hot&active file pages cache ; Cache list是inactive file pages cache.
Segmap tuning中说道 6256083 Need a lightweight file page mapping mechanism to substitute segmap,大概可以在这个例子中显示出来,solaris10比solaris9对于FS cache使用更少的cross calls (mpstat.xcall)。
至于truss cp等看到的mmap64 munmap 等core function就不好理解了。
SunOS sun4u sparc SUNW,Sun-Fire-V440 > ls -altr
total 6874016
-rw-rw—- 1 oracle dba 6078464 Jan 13 23:19 cntrl_lewu_1.dbf
-rw-rw—- 1 oracle dba 6078464 Jan 13 23:19 cntrl_lewu_2.dbftruss cp cntrl_lewu_1.dbf abc
mmap64(0×00000000, 6078464, PROT_READ, MAP_SHARED, 3, 0) = 0xFEC00000
write(4, “\0C2\0\0FFC0\0\0\0\0\0\0″.., 6078464) = 6078464
munmap(0xFEC00000, 6078464) = 0
搞不懂这个mmap64分配的6078464byte内存算是mapped file还是segmap file cache。
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