From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Thu, 21 Aug 2008 21:28:47 -0700 From: Andrew Morton Subject: Re: [RFC][PATCH 1/2] Show quicklist at meminfo Message-Id: <20080821212847.f7fc936b.akpm@linux-foundation.org> In-Reply-To: <20080822100049.F562.KOSAKI.MOTOHIRO@jp.fujitsu.com> References: <20080820113559.f559a411.akpm@linux-foundation.org> <2f11576a0808210036icd9b61eue58049f15381bcc8@mail.gmail.com> <20080822100049.F562.KOSAKI.MOTOHIRO@jp.fujitsu.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: KOSAKI Motohiro Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, cl@linux-foundation.org, tokunaga.keiich@jp.fujitsu.com List-ID: On Fri, 22 Aug 2008 10:05:45 +0900 KOSAKI Motohiro wrote: > > > quicklist_total_size() is racy against cpu hotplug. That's OK for > > > /proc/meminfo purposes (occasional transient inaccuracy?), but will it > > > crash? Not in the current implementation of per_cpu() afaict, but it > > > might crash if we ever teach cpu hotunplug to free up the percpu > > > resources. > > > > First, Quicklist doesn't concern to cpu hotplug at all. > > it is another quicklist problem. > > > > Next, I think it doesn't cause crash. but I haven't any test. > > So, I'll test cpu hotplug/unplug testing today. > > > > I'll report result tommorow. > > OK. > I ran cpu hotplug/unplug coutinuous workload over 12H. > then, system crash doesn't happend. > > So, I believe my patch is cpu unplug safe. err, which patch? I presently have: mm-show-quicklist-memory-usage-in-proc-meminfo.patch mm-show-quicklist-memory-usage-in-proc-meminfo-fix.patch mm-quicklist-shouldnt-be-proportional-to-number-of-cpus.patch mm-quicklist-shouldnt-be-proportional-to-number-of-cpus-fix.patch Is that what you have? I'll consolidate them into two patches and will append them here. Please check. From: KOSAKI Motohiro At present the quicklists store some page for each CPU as a cache. (Each CPU has node_free_pages/16 pages) It is used for page table cache. Then, exit() increase cache, the other hand fork() spent it. So, if apache type (one parent and many child model) middleware run, One CPU process fork(), Other CPU process the middleware work and exit(). At that time, One CPU don't have page table cache at all, Others have maximum caches. QList_max = (#ofCPUs - 1) x Free / 16 => QList_max / (Free + QList_max) = (#ofCPUs - 1) / (16 + #ofCPUs - 1) So, How much quicklist spent memory at maximum case? That is #CPUs proposional because it is per CPU cache but cache amount calculation doesn't use #ofCPUs. Above calculation mean Number of CPUs per node 2 4 8 16 ============================== ==================== QList_max / (Free + QList_max) 5.8% 16% 30% 48% Wow! Quicklist can spent about 50% memory at worst case. More unfortunately, it doesn't have any cache shrinking mechanism. So it cause some wrong thing. 1. End user misunderstand to memory leak happend. => /proc/meminfo should display amount quicklist 2. It can cause OOM killer => Amount of quicklists shouldn't be proportional to number of CPUs. This patch: Quicklists can consume several GB memory. So, if end user can't see how much memory is used, he can fail to understand why a memory leak happend. after this patch applied, /proc/meminfo output following. % cat /proc/meminfo MemTotal: 7701504 kB MemFree: 5159040 kB Buffers: 112960 kB Cached: 337536 kB SwapCached: 0 kB Active: 218944 kB Inactive: 350848 kB Active(anon): 120832 kB Inactive(anon): 0 kB Active(file): 98112 kB Inactive(file): 350848 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 2031488 kB SwapFree: 2031488 kB Dirty: 320 kB Writeback: 0 kB AnonPages: 119488 kB Mapped: 38528 kB Slab: 1595712 kB SReclaimable: 23744 kB SUnreclaim: 1571968 kB PageTables: 14336 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 5882240 kB Committed_AS: 356672 kB VmallocTotal: 17592177655808 kB VmallocUsed: 29056 kB VmallocChunk: 17592177626304 kB Quicklists: 283776 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 262144 kB [akpm@linux-foundation.org: build fix] Signed-off-by: KOSAKI Motohiro Cc: Christoph Lameter Cc: [2.6.25.x, 2.6.26.x] Signed-off-by: Andrew Morton --- fs/proc/proc_misc.c | 7 +++++-- include/linux/quicklist.h | 7 +++++++ 2 files changed, 12 insertions(+), 2 deletions(-) diff -puN fs/proc/proc_misc.c~mm-show-quicklist-memory-usage-in-proc-meminfo fs/proc/proc_misc.c --- a/fs/proc/proc_misc.c~mm-show-quicklist-memory-usage-in-proc-meminfo +++ a/fs/proc/proc_misc.c @@ -24,6 +24,7 @@ #include #include #include +#include #include #include #include @@ -189,7 +190,8 @@ static int meminfo_read_proc(char *page, "Committed_AS: %8lu kB\n" "VmallocTotal: %8lu kB\n" "VmallocUsed: %8lu kB\n" - "VmallocChunk: %8lu kB\n", + "VmallocChunk: %8lu kB\n" + "Quicklists: %8lu kB\n", K(i.totalram), K(i.freeram), K(i.bufferram), @@ -221,7 +223,8 @@ static int meminfo_read_proc(char *page, K(committed), (unsigned long)VMALLOC_TOTAL >> 10, vmi.used >> 10, - vmi.largest_chunk >> 10 + vmi.largest_chunk >> 10, + K(quicklist_total_size()) ); len += hugetlb_report_meminfo(page + len); diff -puN include/linux/quicklist.h~mm-show-quicklist-memory-usage-in-proc-meminfo include/linux/quicklist.h --- a/include/linux/quicklist.h~mm-show-quicklist-memory-usage-in-proc-meminfo +++ a/include/linux/quicklist.h @@ -80,6 +80,13 @@ void quicklist_trim(int nr, void (*dtor) unsigned long quicklist_total_size(void); +#else + +static inline unsigned long quicklist_total_size(void) +{ + return 0; +} + #endif #endif /* LINUX_QUICKLIST_H */ _ From: KOSAKI Motohiro When a test program which does task migration runs, my 8GB box spends 800MB of memory for quicklist. This is not memory leak but doesn't seem good. % cat /proc/meminfo MemTotal: 7701568 kB MemFree: 4724672 kB (snip) Quicklists: 844800 kB because - My machine spec is number of numa node: 2 number of cpus: 8 (4CPU x2 node) total mem: 8GB (4GB x2 node) free mem: about 5GB - Maximum quicklist usage is here Number of CPUs per node 2 4 8 16 ============================== ==================== QList_max / (Free + QList_max) 5.8% 16% 30% 48% - Then, 4.7GB x 16% ~= 880MB. So, Quicklist can use 800MB. So, if following spec machine run that program CPUs: 64 (8cpu x 8node) Mem: 1TB (128GB x8node) Then, quicklist can waste 300GB (= 1TB x 30%). It is too large. So, I don't like cache policies which is proportional to # of cpus. My patch changes the number of caches from: per-cpu-cache-amount = memory_on_node / 16 to per-cpu-cache-amount = memory_on_node / 16 / number_of_cpus_on_node. I think this is reasonable. but even if this patch is applied, quicklist can cache tons of memory on big machine. (Although its patch applied, quicklist can waste 64GB on 1TB server (= 1TB / 16), it is still too much??) test program is below. -------------------------------------------------------------------------------- #define _GNU_SOURCE #include #include #include #include #include #include #include #include #define BUFFSIZE 512 int max_cpu(void) /* get max number of logical cpus from /proc/cpuinfo */ { FILE *fd; char *ret, buffer[BUFFSIZE]; int cpu = 1; fd = fopen("/proc/cpuinfo", "r"); if (fd == NULL) { perror("fopen(/proc/cpuinfo)"); exit(EXIT_FAILURE); } while (1) { ret = fgets(buffer, BUFFSIZE, fd); if (ret == NULL) break; if (!strncmp(buffer, "processor", 9)) cpu = atoi(strchr(buffer, ':') + 2); } fclose(fd); return cpu; } void cpu_bind(int cpu) /* bind current process to one cpu */ { cpu_set_t mask; int ret; CPU_ZERO(&mask); CPU_SET(cpu, &mask); ret = sched_setaffinity(0, sizeof(mask), &mask); if (ret == -1) { perror("sched_setaffinity()"); exit(EXIT_FAILURE); } sched_yield(); /* not necessary */ } #define MMAP_SIZE (10 * 1024 * 1024) /* 10 MB */ #define FORK_INTERVAL 1 /* 1 second */ main(int argc, char *argv[]) { int cpu_max, nextcpu; long pagesize; pid_t pid; /* set max number of logical cpu */ if (argc > 1) cpu_max = atoi(argv[1]) - 1; else cpu_max = max_cpu(); /* get the page size */ pagesize = sysconf(_SC_PAGESIZE); if (pagesize == -1) { perror("sysconf(_SC_PAGESIZE)"); exit(EXIT_FAILURE); } /* prepare parent process */ cpu_bind(0); nextcpu = cpu_max; loop: /* select destination cpu for child process by round-robin rule */ if (++nextcpu > cpu_max) nextcpu = 1; pid = fork(); if (pid == 0) { /* child action */ char *p; int i; /* consume page tables */ p = mmap(0, MMAP_SIZE, PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS, 0, 0); i = MMAP_SIZE / pagesize; while (i-- > 0) { *p = 1; p += pagesize; } /* move to other cpu */ cpu_bind(nextcpu); /* printf("a child moved to cpu%d after mmap().\n", nextcpu); fflush(stdout); */ /* back page tables to pgtable_quicklist */ exit(0); } else if (pid > 0) { /* parent action */ sleep(FORK_INTERVAL); waitpid(pid, NULL, WNOHANG); } goto loop; } [akpm@linux-foundation.org: fix build on sparc64] Signed-off-by: KOSAKI Motohiro Cc: Christoph Lameter Cc: [2.6.25.x, 2.6.26.x] Signed-off-by: Andrew Morton --- mm/quicklist.c | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) diff -puN mm/quicklist.c~mm-quicklist-shouldnt-be-proportional-to-number-of-cpus mm/quicklist.c --- a/mm/quicklist.c~mm-quicklist-shouldnt-be-proportional-to-number-of-cpus +++ a/mm/quicklist.c @@ -26,7 +26,9 @@ DEFINE_PER_CPU(struct quicklist, quickli static unsigned long max_pages(unsigned long min_pages) { unsigned long node_free_pages, max; - struct zone *zones = NODE_DATA(numa_node_id())->node_zones; + int node = numa_node_id(); + struct zone *zones = NODE_DATA(node)->node_zones; + cpumask_t node_cpumask; node_free_pages = #ifdef CONFIG_ZONE_DMA @@ -38,6 +40,10 @@ static unsigned long max_pages(unsigned zone_page_state(&zones[ZONE_NORMAL], NR_FREE_PAGES); max = node_free_pages / FRACTION_OF_NODE_MEM; + + node_cpumask = node_to_cpumask(node); + max /= cpus_weight_nr(node_cpumask); + return max(max, min_pages); } _ -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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