linux中使用free可以查看系統內存使用狀態, 默認單位為k
blue_stone@blueice:~$ freetotal used free shared buffers cachedMem: 2075320 1879172 196148 0 533484 952588-/+ buffers/cache: 393100 1682220Swap: 2008084 0 2008084 |
Mem 行顯示了從系統角度看來內存使用的情況, total是系統可用的內存大小, 數量上等于系統物理內存減去內核保留的內存. buffers和cached是系統用做緩沖的內存. buffers與某個塊設備關聯, 包含了文件系統元數據, 并且跟蹤了塊的變化. cache只包含了文件本身.
-/+ buffers/cache行則從用戶角度顯示內存信息, 可用內存從數量上等于mem行used列值減去buffers和cached內存的大小. 因為buffers和cached是操作系統為加快系統運行而設置的, 當用戶需要時, 可以只接為用戶使用.
top和vmstat也顯示了系統內存的信息, 和free的顯示結果類似.
這些命令都是從/PRoc/meminfo中讀取內存信息.
blue_stone@blueice:~$ cat /proc/meminfoMemTotal: 2075320 kBMemFree: 25016 kBBuffers: 763564 kBCached: 879860 kBSwapCached: 0 kBActive: 1056968 kBInactive: 843136 kBHighTotal: 917440 kBHighFree: 13892 kBLowTotal: 1157880 kBLowFree: 11124 kBSwapTotal: 2008084 kBSwapFree: 2008084 kBDirty: 4708 kBWriteback: 0 kBMapped: 707152 kBSlab: 102728 kBCommitLimit: 3045744 kBCommitted_AS: 691808 kBPageTables: 2936 kBVmallocTotal: 114680 kBVmallocUsed: 14800 kBVmallocChunk: 98800 kB |
關于/proc/meminfo中各行的含意, 在內核源代碼的Documentation/filesystems/proc.txt文件中有敘述，系統的真實內存大小可以用dmesg |grep [mM][eE][mM]看到。
blue_stone@blueice:~$ dmesg |grep [mM][eE][mM]895MB HIGHMEM available.1152MB LOWMEM available.HighMem zone: 229360 pages, LIFO batch:31Memory: 2073292k/2097088k available (1493k kernel code, 21648k reserved, 546k data, 196k init, 917440k highmem)Freeing initrd memory: 1079k freedMEM window: f8000000-f80fffffhighmem bounce pool size: 64 pagesFreeing unused kernel memory: 196k freedehci_hcd 0000:00:10.4: irq 177, io mem 0xf8121000/dev/vmnet: hub 0 does not exist, allocating memory.[fglrx] Maximum main memory to use for locked dma buffers: 1898 MBytes./dev/vmnet: hub 3 does not exist, allocating memory./dev/vmnet: hub 1 does not exist, allocating memory./dev/vmnet: hub 2 does not exist, allocating memory. |
進程使用的內存可以用top, ps來查看top中有3個列 VIRT RES SHR, 標示了進程使用的內存情況, VIRT標識這個進程可以使用的內存總大小, 包括這個進程真實使用的內存, 映射過的文件, 和別的進程共享的內存等. RES標識這個這個進程真實占用內存的大小. SHR標識可以和別的進程共享的內存和庫大小.
/proc/pid/status顯示一個進程的詳細狀態, 下面是一個示例:
blue_stone@blueice:~$ cat /proc/5346/statusName: bashState: S (sleeping)SleepAVG: 98%Tgid: 5346Pid: 5346PPid: 5343TracerPid: 0Uid: 1000 1000 1000 1000Gid: 104 104 104 104FDSize: 256Groups: 6 24 29 44 104 113 1000 1001VmPeak: 6528 kBVmSize: 6528 kBVmLck: 0 kBVmHWM: 1976 kBVmrss: 1976 kBVmData: 752 kBVmStk: 84 kBVmExe: 644 kBVmLib: 1788 kBVmPTE: 16 kBThreads: 1SigQ: 0/4294967295SigPnd: 0000000000000000ShdPnd: 0000000000000000SigBlk: 0000000000000000SigIgn: 0000000000384004SigCgt: 000000004b813efbCapInh: 0000000000000000CapPrm: 0000000000000000CapEff: 0000000000000000 |
VmSize即為該進程內存總大小, 和top輸出中的VIRT一致。
