Messages in this thread Patches in this message | | | Date | Wed, 22 Nov 2006 15:51:06 +0800 | From | Aubrey <> | Subject | The VFS cache is not freed when there is not enough free memory to allocate |
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Hi all,
We are working on the blackfin uClinux platform and we encountered the following problem. The attached patch can work around this issue and I post it here to find better solution.
Here is a test application: --------------------------------------------------------------------------------------------- #include <stdio.h> #include <stdlib.h> #define N 8
int main (void){ void *p[N]; int i;
printf("Alloc %d MB !\n", N);
for (i = 0; i < N; i++) { p[i] = malloc(1024 * 1024); if (p[i] == NULL) printf("alloc failed\n"); }
printf("alloc successful \n"); for (i = 0; i < N; i++) free(p[i]); }
When there is not enough free memory to allocate: ============================== root:/mnt> cat /proc/meminfo MemTotal: 54196 kB MemFree: 5520 kB <== only 5M free Buffers: 76 kB Cached: 44696 kB <== cache eat 40MB SwapCached: 0 kB Active: 21092 kB Inactive: 23680 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 54196 kB LowFree: 5520 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 0 kB Writeback: 0 kB AnonPages: 0 kB Mapped: 0 kB Slab: 3720 kB PageTables: 0 kB NFS_Unstable: 0 kB Bounce: 0 kB CommitLimit: 27096 kB Committed_AS: 0 kB VmallocTotal: 0 kB VmallocUsed: 0 kB VmallocChunk: 0 kB ==========================================
I run the test application and get the following message: --------------------------------------- root:/mnt> ./t Alloc 8 MB ! t: page allocation failure. order:9, mode:0x40d0 Hardware Trace: 0 Target : <0x00004de0> { _dump_stack + 0x0 } Source : <0x0003054a> { ___alloc_pages + 0x17e } 1 Target : <0x0003054a> { ___alloc_pages + 0x17e } Source : <0x0000dbc2> { _printk + 0x16 } 2 Target : <0x0000dbbe> { _printk + 0x12 } Source : <0x0000da4e> { _vprintk + 0x1a2 } 3 Target : <0x0000da42> { _vprintk + 0x196 } Source : <0xffa001ea> { __common_int_entry + 0xd8 } 4 Target : <0xffa00188> { __common_int_entry + 0x76 } Source : <0x000089bc> { _return_from_int + 0x58 } 5 Target : <0x000089bc> { _return_from_int + 0x58 } Source : <0x00008992> { _return_from_int + 0x2e } 6 Target : <0x00008964> { _return_from_int + 0x0 } Source : <0xffa00184> { __common_int_entry + 0x72 } 7 Target : <0xffa00182> { __common_int_entry + 0x70 } Source : <0x00012682> { __local_bh_enable + 0x56 } 8 Target : <0x0001266c> { __local_bh_enable + 0x40 } Source : <0x0001265c> { __local_bh_enable + 0x30 } 9 Target : <0x00012654> { __local_bh_enable + 0x28 } Source : <0x00012644> { __local_bh_enable + 0x18 } 10 Target : <0x0001262c> { __local_bh_enable + 0x0 } Source : <0x000128e0> { ___do_softirq + 0x94 } 11 Target : <0x000128d8> { ___do_softirq + 0x8c } Source : <0x000128b8> { ___do_softirq + 0x6c } 12 Target : <0x000128aa> { ___do_softirq + 0x5e } Source : <0x0001666a> { _run_timer_softirq + 0x82 } 13 Target : <0x000165fc> { _run_timer_softirq + 0x14 } Source : <0x00023eb8> { _hrtimer_run_queues + 0xe8 } 14 Target : <0x00023ea6> { _hrtimer_run_queues + 0xd6 } Source : <0x00023e70> { _hrtimer_run_queues + 0xa0 } 15 Target : <0x00023e68> { _hrtimer_run_queues + 0x98 } Source : <0x00023eae> { _hrtimer_run_queues + 0xde } Stack from 015a7dcc: 00000001 0003054e 00000000 00000001 000040d0 0013c70c 00000009 000040d0 00000000 00000080 00000000 000240d0 00000000 015a6000 015a6000 015a6000 00000010 00000000 00000001 00036e12 00000000 0023f8e0 00000073 00191e40 00000020 0023e9a0 000040d0 015afea9 015afe94 00101fff 000040d0 0023e9a0 00000010 00101fff 000370de 00000000 0363d3e0 00000073 0000ffff 04000021 00000000 00101000 00187af0 00035b44 00000000 00035e40 00000000 00000000 Call Trace: [<0000fffe>] _do_exit+0x12e/0x7cc [<00004118>] _sys_mmap+0x54/0x98 [<00101000>] _fib_create_info+0x670/0x780 [<00008828>] _system_call+0x68/0xba [<000040c4>] _sys_mmap+0x0/0x98 [<0000fffe>] _do_exit+0x12e/0x7cc [<00008000>] _cplb_mgr+0x8/0x2e8 [<00101000>] _fib_create_info+0x670/0x780 [<00101000>] _fib_create_info+0x670/0x780
Mem-info: DMA per-cpu: cpu 0 hot: high 18, batch 3 used:5 cpu 0 cold: high 6, batch 1 used:5 DMA32 per-cpu: empty Normal per-cpu: empty HighMem per-cpu: empty Free pages: 21028kB (0kB HighMem) Active:2549 inactive:3856 dirty:0 writeback:0 unstable:0 free:5257 slab:1833 mapped:0 pagetables:0 DMA free:21028kB min:948kB low:1184kB high:1420kB active:10196kB inactive:15424kB present:56320kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 DMA32 free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 Normal free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 HighMem free:0kB min:128kB low:128kB high:128kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 DMA: 43*4kB 35*8kB 28*16kB 17*32kB 18*64kB 20*128kB 16*256kB 11*512kB 6*1024kB 0*2048kB 0*4096kB 0*8192kB 0*16384kB 0*32768kB = 21028kB DMA32: empty Normal: empty HighMem: empty 14080 pages of RAM 5285 free pages 531 reserved pages 11 pages shared 0 pages swap cached Allocation of length 1052672 from process 57 failed DMA per-cpu: cpu 0 hot: high 18, batch 3 used:5 cpu 0 cold: high 6, batch 1 used:5 DMA32 per-cpu: empty Normal per-cpu: empty HighMem per-cpu: empty Free pages: 21028kB (0kB HighMem) Active:2549 inactive:3856 dirty:0 writeback:0 unstable:0 free:5257 slab:1833 mapped:0 pagetables:0 DMA free:21028kB min:948kB low:1184kB high:1420kB active:10196kB inactive:15424kB present:56320kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 DMA32 free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 Normal free:0kB min:0kB low:0kB high:0kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 HighMem free:0kB min:128kB low:128kB high:128kB active:0kB inactive:0kB present:0kB pages_scanned:0 all_unreclaimable? no lowmem_reserve[]: 0 0 0 0 DMA: 43*4kB 35*8kB 28*16kB 17*32kB 18*64kB 20*128kB 16*256kB 11*512kB 6*1024kB 0*2048kB 0*4096kB 0*8192kB 0*16384kB 0*32768kB = 21028kB DMA32: empty Normal: empty HighMem: empty -----------------------------
When there is no enough free memory, kernel crash instead of freeing VFS cache, no matter how big the value of /proc/sys/vm/vfs_cache_pressure is set.
Here is my patch, ===================================== From a8a03f1fed672cc310feb3f5fafdc9e0e7a6546f Mon Sep 17 00:00:00 2001 From: Aubrey.Li <aubrey.li@analog.com> Date: Wed, 22 Nov 2006 15:10:18 +0800 Subject: [PATCH] Drop VFS cache when there is not enough free memory to allocate
Signed-off-by: Aubrey.Li <aubrey.li@analog.com> --- mm/page_alloc.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bf2f6cf..62559fd 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1039,6 +1039,11 @@ restart: if (page) goto got_pg;
+#if defined(CONFIG_EMBEDDED) && !defined(CONFIG_MMU) + drop_pagecache(); + drop_slab(); +#endif + /* This allocation should allow future memory freeing. */
if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE))) -- 1.4.2 ======================================== The patch drop the page cache and slab and then give a new chance to get more free pages. Applied this patch, my test application can allocate memory sucessfully and drop the cache and slab as well. See below: ================================ root:/mnt> ./t Alloc 8 MB ! alloc successful root:/mnt> cat /proc/meminfo MemTotal: 54196 kB MemFree: 43684 kB Buffers: 36 kB Cached: 440 kB SwapCached: 0 kB Active: 32 kB Inactive: 432 kB HighTotal: 0 kB HighFree: 0 kB LowTotal: 54196 kB LowFree: 43684 kB SwapTotal: 0 kB SwapFree: 0 kB Dirty: 8 kB Writeback: 0 kB AnonPages: 0 kB Mapped: 0 kB Slab: 9812 kB PageTables: 0 kB NFS_Unstable: 0 kB Bounce: 0 kB CommitLimit: 27096 kB Committed_AS: 0 kB VmallocTotal: 0 kB VmallocUsed: 0 kB VmallocChunk: 0 kB ============================= I know performance is important for linux, and VFS cache obviously improve the performance when implement file operation. But for embedded system, we'll try our best to make the application executable rather than hanging system to guarantee the system performance.
Any suggestions and solutions are really appreciated!
Thanks, -Aubrey From a8a03f1fed672cc310feb3f5fafdc9e0e7a6546f Mon Sep 17 00:00:00 2001 From: Aubrey.Li <aubrey@SUSE10.ANALOG> Date: Wed, 22 Nov 2006 15:10:18 +0800 Subject: [PATCH] Drop VFS cache when there is not enough free memory to allocate
Signed-off-by: Aubrey.Li <aubrey@SUSE10.ANALOG> --- mm/page_alloc.c | 5 +++++ 1 files changed, 5 insertions(+), 0 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bf2f6cf..62559fd 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1039,6 +1039,11 @@ restart: if (page) goto got_pg; +#if defined(CONFIG_EMBEDDED) && !defined(CONFIG_MMU) + drop_pagecache(); + drop_slab(); +#endif + /* This allocation should allow future memory freeing. */ if (((p->flags & PF_MEMALLOC) || unlikely(test_thread_flag(TIF_MEMDIE))) -- 1.4.2
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