Re: Memory leak in 2.4.33-pre1?

From: Willy TARREAU
Date: Tue Feb 14 2006 - 16:41:54 EST

On Tue, Feb 14, 2006 at 09:21:36AM +0100, Yoss wrote:
> On Tue, Feb 14, 2006 at 01:05:30AM +0100, Willy Tarreau wrote:
> > You don't have to worry. Simply check /proc/slabinfo, you'll see plenty
> > of memory used by dentry_cache and inode_cache and that's expected. This
> > memory will be reclaimed when needed (for instance by calls to malloc()).
>
> I downgraded hernel to 2.4.33 last night.

I presume you mean 2.4.32 here.

> So there is no slabinfo from that problem now. But thank you for reply.
> Why is this memory not showed somewhere in top or free?

I don't know, it's some gray area for me too, it's just that I'm used to
this behaviour. I even have a program that I run to free it when I want
to prioritize disk cache usage over dentry cache (appended to this mail).

For instance, I've booted my notebook to work on it. 3 minutes after the boot
has completed, slocate starts indexing files (I wait 3 minutes to speed up
services start). Now that slocate has ended its job, here is what a few tools
have to say about my memory usage :

$ free
total used free shared buffers cached
Mem: 514532 509576 4956 0 25836 5808
-/+ buffers/cache: 477932 36600
Swap: 312316 1436 310880

It even managed to swap !

$ vmstat 1
procs -----------memory---------- ---swap-- -----io---- --system-- ----cpu----
r b swpd free buff cache si so bi bo in cs us sy id wa
0 0 1436 4908 25860 5824 0 1 1213 39 536 586 2 7 90 0
0 0 1436 4904 25860 5824 0 0 0 0 254 16 0 0 100 0

$ top
top - 22:32:47 up 12 min, 1 user, load average: 0.12, 0.52, 0.34
Tasks: 44 total, 1 running, 43 sleeping, 0 stopped, 0 zombie
Cpu(s): 0.1% user, 7.2% system, 2.2% nice, 90.5% idle
Mem: 514532k total, 510076k used, 4456k free, 25900k buffers
Swap: 312316k total, 1436k used, 310880k free, 6112k cached

$ cat /proc/meminfo
total: used: free: shared: buffers: cached:
Mem: 526880768 522194944 4685824 0 26521600 6946816
Swap: 319811584 1470464 318341120
MemTotal: 514532 kB
MemFree: 4576 kB
MemShared: 0 kB
Buffers: 25900 kB
Cached: 6132 kB
SwapCached: 652 kB
Active: 20052 kB
Inactive: 12664 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 514532 kB
LowFree: 4576 kB
SwapTotal: 312316 kB
SwapFree: 310880 kB

$ cat /proc/slabinfo
slabinfo - version: 1.1
kmem_cache 81 108 108 3 3 1
urb_priv 0 0 64 0 0 1
ip_fib_hash 10 113 32 1 1 1
clip_arp_cache 0 0 128 0 0 1
mpr 0 0 16 0 0 1
label 0 0 32 0 0 1
tcp_tw_bucket 0 0 96 0 0 1
tcp_bind_bucket 9 113 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 2 20 192 1 1 1
arp_cache 1 40 96 1 1 1
ip_arpf_cache 0 0 128 0 0 1
blkdev_requests 5120 5120 96 128 128 1
xfs_chashlist 0 0 20 0 0 1
xfs_ili 0 0 140 0 0 1
xfs_ifork 0 0 56 0 0 1
xfs_efi_item 0 0 260 0 0 1
xfs_efd_item 0 0 260 0 0 1
xfs_buf_item 0 0 148 0 0 1
xfs_dabuf 0 0 16 0 0 1
xfs_da_state 0 0 336 0 0 1
xfs_trans 0 0 592 0 0 2
xfs_inode 0 0 376 0 0 1
xfs_btree_cur 0 0 132 0 0 1
xfs_bmap_free_item 0 0 12 0 0 1
xfs_buf_t 0 0 192 0 0 1
linvfs_icache 0 0 320 0 0 1
ext2_xattr 0 0 44 0 0 1
journal_head 0 0 48 0 0 1
revoke_table 0 0 12 0 0 1
revoke_record 0 0 32 0 0 1
ext3_xattr 0 0 44 0 0 1
eventpoll pwq 0 0 36 0 0 1
eventpoll epi 0 0 96 0 0 1
dnotify_cache 0 0 20 0 0 1
file_lock_cache 3 42 92 1 1 1
fasync_cache 0 0 16 0 0 1
uid_cache 6 113 32 1 1 1
skbuff_head_cache 207 220 192 11 11 1
sock 34 36 896 9 9 1
sigqueue 0 29 132 0 1 1
kiobuf 0 0 64 0 0 1
cdev_cache 60 177 64 3 3 1
bdev_cache 8 59 64 1 1 1
mnt_cache 16 59 64 1 1 1
inode_cache 751083 751096 480 93886 93887 1
dentry_cache 602570 607530 128 20251 20251 1
filp 334 360 128 12 12 1
names_cache 0 2 4096 0 2 1
buffer_head 7084 9440 96 234 236 1
mm_struct 32 48 160 2 2 1
vm_area_struct 2362 2600 96 62 65 1
fs_cache 31 113 32 1 1 1
files_cache 32 36 416 4 4 1
signal_act 40 42 1312 14 14 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 8 8 32768 8 8 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 4 4 8192 4 4 2
size-4096(DMA) 0 0 4096 0 0 1
size-4096 69 69 4096 69 69 1
size-2048(DMA) 0 0 2048 0 0 1
size-2048 213 216 2048 107 108 1
size-1024(DMA) 0 0 1024 0 0 1
size-1024 51 52 1024 13 13 1
size-512(DMA) 0 0 512 0 0 1
size-512 183 184 512 23 23 1
size-256(DMA) 0 0 256 0 0 1
size-256 51 60 256 4 4 1
size-128(DMA) 3 30 128 1 1 1
size-128 1574 1620 128 54 54 1
size-64(DMA) 0 0 64 0 0 1
size-64 38450 38468 64 652 652 1
size-32(DMA) 51 113 32 1 1 1
size-32 76440 78309 32 693 693 1

Have you noticed dentry_cache and inode_cache above ?
Now I will allocate (and touch) 500000 kB of ram (OK it speaks french) :

$ ~/dev/freemem 500000
Liberation de 500000 ko de ram en cours
500000 k alloues (blocs de 1k)
Memoire liberee.

$ free
total used free shared buffers cached
Mem: 514532 22368 492164 0 1324 4276
-/+ buffers/cache: 16768 497764
Swap: 312316 4252 308064

$ grep cache /proc/slabinfo
kmem_cache 81 108 108 3 3 1
clip_arp_cache 0 0 128 0 0 1
inet_peer_cache 0 0 64 0 0 1
ip_dst_cache 2 20 192 1 1 1
arp_cache 1 40 96 1 1 1
ip_arpf_cache 0 0 128 0 0 1
linvfs_icache 0 0 320 0 0 1
dnotify_cache 0 0 20 0 0 1
file_lock_cache 3 42 92 1 1 1
fasync_cache 0 0 16 0 0 1
uid_cache 6 113 32 1 1 1
skbuff_head_cache 208 220 192 11 11 1
cdev_cache 17 177 64 3 3 1
bdev_cache 8 59 64 1 1 1
mnt_cache 16 59 64 1 1 1
inode_cache 321 768 480 96 96 1
dentry_cache 338 1740 128 58 58 1
names_cache 0 2 4096 0 2 1
fs_cache 31 113 32 1 1 1
files_cache 32 36 416 4 4 1

Have you noticed the difference ? So the memory is not wasted at all. It's
just reported as 'used'.

> > If you don't believe me, simply allocate 1 GB in a process, then free it.
>
> If that what you said is rigth, day after tomorow I'll have the same
> situation - only thing I have changed is kernel. So we'll see. :)

If you encounter it, simply run the tool below with a size in kB. Warning!
a wrong parameter associated with improper ulimit will hang your system !
Ask it to allocate what you *know* you can free (eg: the swapfree space).

> --
> Bart?omiej Butyn aka Yoss
> Nie ma tego z?ego co by na gorsze nie wysz?o.

Regards,
Willy

--- begin freemem.c ---
/* it's old and ugly but still useful */
#include <stdio.h>

main(int argc, char **argv) {

unsigned long int i,k=0, max;
char *p;


if (argc>1)
max=atol(argv[1]);
else
max=0xffffffff;

printf("Liberation de %lu ko de ram en cours\n",max);
/* allocation de blocs de 1 Mo */
while (((p=(char *)malloc(1048576))!=NULL) && (k+1024<=max)) {
for (i=0;i<256;p[4096*i++]=0); /* utilisation du bloc */
k+=1024;
fprintf(stderr,"\r%d k alloues (blocs de 1M)",k);
}
while (((p=(char *)malloc(65536))!=NULL) && (k+64<=max)) {
for (i=0;i<16;p[4096*i++]=0); /* utilisation du bloc */
k+=64;
fprintf(stderr,"\r%d k alloues (blocs de 64k)",k);
}
while (((p=(char *)malloc(1024))!=NULL) && (k+1<=max)) {
for (i=0;i<16;p[64*i++]=0); /* utilisation du bloc */
k+=1;
fprintf(stderr,"\r%d k alloues (blocs de 1k) ",k);
}
fprintf(stderr,"\nMemoire liberee.\n");
exit(0);
}
--- end freemem.c ---

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