I think find a ramdisk bug of 2.4.4 kernel -- ramdisk
use both buffers and cached mem of the same size, thus
double the mem use.
mke2fs -m0 /dev/ram1
mount /dev/ram1 /mnt
dd if=/dev/zero of=/mnt/data bs=1k count=110000
cat /proc/meminfo will see that both buffers and
cached mem increase about 110M of size. More worse,
the cached mem won't be released untile the ramdisk
be umounted. I attach the meminfo and slabinfo before
and after data transfer below.
This problem is not found on redhat7.1 of 2.4.2 kernel and
redhat7.0 of 2.2.16 kernel.
meminfo before transfer data to ramdisk:
total: used: free: shared: buffers: cached:
Mem: 260780032 17068032 243712000 0 4943872 6971392
Swap: 139788288 0 139788288
MemTotal: 254668 kB
MemFree: 238000 kB
MemShared: 0 kB
Buffers: 4828 kB
Cached: 6808 kB
Active: 8376 kB
Inact_dirty: 3260 kB
Inact_clean: 0 kB
Inact_target: 108 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 254668 kB
LowFree: 238000 kB
SwapTotal: 136512 kB
SwapFree: 136512 kB
meminfo after transfer data to ramdisk:
total: used: free: shared: buffers: cached:
Mem: 260780032 258662400 2117632 0 117317632 115666944
Swap: 139788288 2048000 137740288
MemTotal: 254668 kB
MemFree: 2068 kB
MemShared: 0 kB
Buffers: 114568 kB
Cached: 112956 kB
Active: 224960 kB
Inact_dirty: 52 kB
Inact_clean: 2512 kB
Inact_target: 1924 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 254668 kB
LowFree: 2068 kB
SwapTotal: 136512 kB
SwapFree: 134512 kB
slabinfo before transfer data to ramdisk:
slabinfo - version: 1.1
kmem_cache 58 78 100 2 2 1
ip_fib_hash 17 113 32 1 1 1
ip_conntrack 3 11 352 1 1 1
ip_mrt_cache 0 0 96 0 0 1
tcp_tw_bucket 0 0 96 0 0 1
tcp_bind_bucket 1 113 32 1 1 1
tcp_open_request 0 0 64 0 0 1
inet_peer_cache 0 0 64 0 0 1
ip_dst_cache 7 20 192 1 1 1
arp_cache 0 0 128 0 0 1
nfs_read_data 0 0 384 0 0 1
nfs_write_data 0 0 384 0 0 1
nfs_page 0 0 96 0 0 1
blkdev_requests 2048 2080 96 52 52 1
dnotify cache 0 0 20 0 0 1
file lock cache 1 42 92 1 1 1
fasync cache 0 0 16 0 0 1
uid_cache 1 113 32 1 1 1
skbuff_head_cache 93 96 160 4 4 1
sock 9 18 832 1 2 2
inode_cache 237 240 480 30 30 1
bdev_cache 7 59 64 1 1 1
sigqueue 0 29 132 0 1 1
dentry_cache 434 450 128 15 15 1
dquot 0 0 96 0 0 1
filp 77 80 96 2 2 1
names_cache 0 8 4096 0 8 1
buffer_head 5959 5960 96 149 149 1
mm_struct 12 30 128 1 1 1
vm_area_struct 153 177 64 3 3 1
fs_cache 11 59 64 1 1 1
files_cache 11 18 416 2 2 1
signal_act 13 15 1312 5 5 1
size-131072(DMA) 0 0 131072 0 0 32
size-131072 0 0 131072 0 0 32
size-65536(DMA) 0 0 65536 0 0 16
size-65536 0 0 65536 0 0 16
size-32768(DMA) 0 0 32768 0 0 8
size-32768 0 0 32768 0 0 8
size-16384(DMA) 0 0 16384 0 0 4
size-16384 0 0 16384 0 0 4
size-8192(DMA) 0 0 8192 0 0 2
size-8192 0 0 8192 0 0 2
size-4096(DMA) 0 0 4096 0 0 1
size-4096 19 19 4096 19 19 1
size-2048(DMA) 0 0 2048 0 0 1
size-2048 88 90 2048 45 45 1
size-1024(DMA) 0 0 1024 0 0 1
size-1024 29 32 1024 8 8 1
size-512(DMA) 0 0 512 0 0 1
size-512 21 24 512 3 3 1
size-256(DMA) 0 0 256 0 0 1
size-256 19 45 256 3 3 1
size-128(DMA) 0 0 128 0 0 1
size-128 561 570 128 19 19 1
size-64(DMA) 0 0 64 0 0 1
size-64 95 118 64 2 2 1
size-32(DMA) 0 0 32 0 0 1
size-32 343 452 32 4 4 1
slabinfo after transfer data to ramdisk:
slabinfo - version: 1.1
kmem_cache 58 78 100 2 2 1
ip_fib_hash 17 113 32 1 1 1
ip_conntrack 1 11 352 1 1 1
ip_mrt_cache 0 0 96 0 0 1
tcp_tw_bucket 0 0 96 0 0 1
tcp_bind_bucket 1 113 32 1 1 1
tcp_open_request 0 0 64 0 0 1
inet_peer_cache 0 0 64 0 0 1
ip_dst_cache 7 20 192 1 1 1
arp_cache 0 0 128 0 0 1
nfs_read_data 0 0 384 0 0 1
nfs_write_data 0 0 384 0 0 1
nfs_page 0 0 96 0 0 1
blkdev_requests 2048 2080 96 52 52 1
dnotify cache 0 0 20 0 0 1
file lock cache 1 42 92 1 1 1
fasync cache 0 0 16 0 0 1
uid_cache 1 113 32 1 1 1
skbuff_head_cache 93 96 160 4 4 1
sock 9 9 832 1 1 2
inode_cache 81 200 480 25 25 1
bdev_cache 3 59 64 1 1 1
sigqueue 0 29 132 0 1 1
dentry_cache 73 330 128 11 11 1
dquot 0 0 96 0 0 1
filp 77 80 96 2 2 1
names_cache 0 2 4096 0 2 1
buffer_head 224544 224880 96 5622 5622 1
mm_struct 12 30 128 1 1 1
vm_area_struct 153 177 64 3 3 1
fs_cache 11 59 64 1 1 1
files_cache 11 18 416 2 2 1
signal_act 13 15 1312 5 5 1
size-131072(DMA) 0 0 131072 0 0 32
size-131072 0 0 131072 0 0 32
size-65536(DMA) 0 0 65536 0 0 16
size-65536 0 0 65536 0 0 16
size-32768(DMA) 0 0 32768 0 0 8
size-32768 0 0 32768 0 0 8
size-16384(DMA) 0 0 16384 0 0 4
size-16384 0 0 16384 0 0 4
size-8192(DMA) 0 0 8192 0 0 2
size-8192 0 0 8192 0 0 2
size-4096(DMA) 0 0 4096 0 0 1
size-4096 19 19 4096 19 19 1
size-2048(DMA) 0 0 2048 0 0 1
size-2048 88 90 2048 45 45 1
size-1024(DMA) 0 0 1024 0 0 1
size-1024 29 32 1024 8 8 1
size-512(DMA) 0 0 512 0 0 1
size-512 21 24 512 3 3 1
size-256(DMA) 0 0 256 0 0 1
size-256 19 45 256 3 3 1
size-128(DMA) 0 0 128 0 0 1
size-128 561 570 128 19 19 1
size-64(DMA) 0 0 64 0 0 1
size-64 87 118 64 2 2 1
size-32(DMA) 0 0 32 0 0 1
size-32 199 452 32 4 4 1
Best,
Zeng Yu
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