linux内存耗尽的分析

　　

在测试NAS性能，用fstest长时间写，分析性能变差的原因，发现server主机内存使用率很高。

1．首先查看内存

#top-Mtop-14:43:12up14days,6min,1user,loadaverage:8.36,8.38,8.41Tasks:total,1running,sleeping,0stopped,0zombieCpu(s):0.0%us,0.2%sy,0.0%ni,99.0%id,0.7%wa,0.0%hi,0.0%si,0.0%stMem:63.Gtotal,62.Gused,.Mfree,33.MbuffersSwap:.Mtotal,0.kused,.Mfree,48.GcachedPIDUSERPRNIVIRTRESSHRS%CPU%MEMTIME+COMMANDroot200S2.00.00:25.52ksoftirqd/rootR2.00.00:00.01toproot200D2.00.:54.02nfsdroot0-20S2.00.00:11.89kworker/5:1H1rootS0.00.00:01.88init.....

发现内存基本用完，究竟是什么进程占用？top命令发现排名第一的%MEM才零点几。

2.通过vmstat-m命令查看内核空间的内存使用。

15161#vmstat-mCacheNumTotalSizePagesxfs_dqtrxxfs_dquot047xfs_buf914252133fstrm_itemxfs_mru_cache_elemxfs_ilixfs_inode756584xfs_efi_itemxfs_efd_itemxfs_buf_item7xfs_log_item_descxfs_transxfs_iforkxfs_da_statexfs_btree_curxfs_bmap_free_itemxfs_log_ticketxfs_ioendrbd_segment_namerbd_obj_request2rbd_img_request2ceph_osd_requestceph_msg_dataceph_msg7nfsd_drcnfsd4_delegationsnfsd4_stateidsnfsd4_files802130nfsd4_lockownersnfsd4_openownersrpc_inode_cacherpc_buffersrpc_tasksfib6_nodespte_list_descext4_groupinfo_4kext4_inode_cacheext4_xattrext4_free_dataext4_allocation_contextext4_prealloc_spaceext4_system_zoneCacheNumTotalSizePagesext4_io_endext4_extent_statusjbd2_transaction_s303615jbd2_inode........

发现这两项值很高：xfs_ilixfs_inode占用了大量的内存。

3.使用slabtop命令查看内核slab缓冲区信息

#slabtop-sc

headActive/TotalObjects(%used):/(89.2%)Active/TotalSlabs(%used):/(.0%)Active/TotalCaches(%used):/(61.2%)Active/TotalSize(%used):.43K/.05K(88.1%)Minimum/Average/MaximumObject:0.02K/0.36K/.00KOBJSACTIVEUSEOBJSIZESLABSOBJ/SLABCACHESIZENAME8480756589%1.00KKxfs_inode%0.22KKxfs_ili

xfs_ili占用1965kxfs_inode占用8480K，但他们究竟是什么东东？猜测是nas/rbd卷的文件系统缓存信息。xfs_inode看字面意思是xfs文件系统的inode信息。

搜了下xfs_ili，只搜到内核代码片段。

15161xfs_inode_zone=kmem_zone_init_flags(sizeof(xfs_inode_t),xfs_inode,KM_ZONE_HWALIGN

KM_ZONE_RECLAIM

KM_ZONE_SPREAD,xfs_fs_inode_init_once);1if(!xfs_inode_zone)gotoout_destroy_efi_zone;xfs_ili_zone=kmem_zone_init_flags(sizeof(xfs_inode_log_item_t),xfs_ili,KM_ZONE_SPREAD,NULL);28typedefstructxfs_inode_log_item{29xfs_log_item_tili_item;/*







































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