From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753362Ab2KUJCs (ORCPT ); Wed, 21 Nov 2012 04:02:48 -0500 Received: from mga03.intel.com ([143.182.124.21]:20315 "EHLO mga03.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751876Ab2KUJCo (ORCPT ); Wed, 21 Nov 2012 04:02:44 -0500 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="4.83,291,1352102400"; d="h'?c'?scan'208";a="170909450" Date: Wed, 21 Nov 2012 17:02:04 +0800 From: Fengguang Wu To: Jaegeuk Hanse Cc: metin d , Jan Kara , "linux-kernel@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: Problem in Page Cache Replacement Message-ID: <20121121090204.GA9064@localhost> References: <1353433362.85184.YahooMailNeo@web141101.mail.bf1.yahoo.com> <20121120182500.GH1408@quack.suse.cz> <1353485020.53500.YahooMailNeo@web141104.mail.bf1.yahoo.com> <1353485630.17455.YahooMailNeo@web141106.mail.bf1.yahoo.com> <50AC9220.70202@gmail.com> MIME-Version: 1.0 Content-Type: multipart/mixed; boundary="FCuugMFkClbJLl1L" Content-Disposition: inline In-Reply-To: <50AC9220.70202@gmail.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org --FCuugMFkClbJLl1L Content-Type: text/plain; charset=us-ascii Content-Disposition: inline On Wed, Nov 21, 2012 at 04:34:40PM +0800, Jaegeuk Hanse wrote: > Cc Fengguang Wu. > > On 11/21/2012 04:13 PM, metin d wrote: > >> Curious. Added linux-mm list to CC to catch more attention. If you run > >>echo 1 >/proc/sys/vm/drop_caches does it evict data-1 pages from memory? > >I'm guessing it'd evict the entries, but am wondering if we could run any more diagnostics before trying this. > > > >We regularly use a setup where we have two databases; one gets used frequently and the other one about once a month. It seems like the memory manager keeps unused pages in memory at the expense of frequently used database's performance. > >My understanding was that under memory pressure from heavily > >accessed pages, unused pages would eventually get evicted. Is there > >anything else we can try on this host to understand why this is > >happening? We may debug it this way. 1) run 'fadvise data-2 0 0 dontneed' to drop data-2 cached pages (please double check via /proc/vmstat whether it does the expected work) 2) run 'page-types -r' with root, to view the page status for the remaining pages of data-1 The fadvise tool comes from Andrew Morton's ext3-tools. (source code attached) Please compile them with options "-Dlinux -I. -D_GNU_SOURCE -D_FILE_OFFSET_BITS=64 -D_LARGEFILE64_SOURCE" page-types can be found in the kernel source tree tools/vm/page-types.c Sorry that sounds a bit twisted.. I do have a patch to directly dump page cache status of a user specified file, however it's not upstreamed yet. Thanks, Fengguang > >On Tue 20-11-12 09:42:42, metin d wrote: > >>I have two PostgreSQL databases named data-1 and data-2 that sit on the > >>same machine. Both databases keep 40 GB of data, and the total memory > >>available on the machine is 68GB. > >> > >>I started data-1 and data-2, and ran several queries to go over all their > >>data. Then, I shut down data-1 and kept issuing queries against data-2. > >>For some reason, the OS still holds on to large parts of data-1's pages > >>in its page cache, and reserves about 35 GB of RAM to data-2's files. As > >>a result, my queries on data-2 keep hitting disk. > >> > >>I'm checking page cache usage with fincore. When I run a table scan query > >>against data-2, I see that data-2's pages get evicted and put back into > >>the cache in a round-robin manner. Nothing happens to data-1's pages, > >>although they haven't been touched for days. > >> > >>Does anybody know why data-1's pages aren't evicted from the page cache? > >>I'm open to all kind of suggestions you think it might relate to problem. > > Curious. Added linux-mm list to CC to catch more attention. If you run > >echo 1 >/proc/sys/vm/drop_caches > > does it evict data-1 pages from memory? > > > >>This is an EC2 m2.4xlarge instance on Amazon with 68 GB of RAM and no > >>swap space. The kernel version is: > >> > >>$ uname -r > >>3.2.28-45.62.amzn1.x86_64 > >>Edit: > >> > >>and it seems that I use one NUMA instance, if you think that it can a problem. > >> > >>$ numactl --hardware > >>available: 1 nodes (0) > >>node 0 cpus: 0 1 2 3 4 5 6 7 > >>node 0 size: 70007 MB > >>node 0 free: 360 MB > >>node distances: > >>node 0 > >> 0: 10 --FCuugMFkClbJLl1L Content-Type: text/x-csrc; charset=us-ascii Content-Disposition: attachment; filename="fadvise.c" #include #include #include #include #include #include #include "fadvise.h" char *progname; static void usage(void) { fprintf(stderr, "Usage: %s filename offset length advice [loops]\n", progname); fprintf(stderr, " advice: normal sequential willneed noreuse " "dontneed asyncwrite writewait\n"); exit(1); } int main(int argc, char *argv[]) { int c; int fd; char *sadvice; char *filename; loff_t offset; unsigned long length; int advice = 0; int ret; int loops = 1; progname = argv[0]; while ((c = getopt(argc, argv, "")) != -1) { switch (c) { } } if (optind == argc) usage(); filename = argv[optind++]; if (optind == argc) usage(); offset = strtoull(argv[optind++], NULL, 0); if (optind == argc) usage(); length = strtol(argv[optind++], NULL, 0); if (optind == argc) usage(); sadvice = argv[optind++]; if (optind != argc) loops = strtol(argv[optind++], NULL, 0); if (optind != argc) usage(); if (!strcmp(sadvice, "normal")) advice = POSIX_FADV_NORMAL; else if (!strcmp(sadvice, "sequential")) advice = POSIX_FADV_SEQUENTIAL; else if (!strcmp(sadvice, "willneed")) advice = POSIX_FADV_WILLNEED; else if (!strcmp(sadvice, "noreuse")) advice = POSIX_FADV_NOREUSE; else if (!strcmp(sadvice, "dontneed")) advice = POSIX_FADV_DONTNEED; else if (!strcmp(sadvice, "asyncwrite")) advice = LINUX_FADV_ASYNC_WRITE; else if (!strcmp(sadvice, "writewait")) advice = LINUX_FADV_WRITE_WAIT; else usage(); fd = open(filename, O_RDONLY); if (fd < 0) { fprintf(stderr, "%s: cannot open `%s': %s\n", progname, filename, strerror(errno)); exit(1); } while (loops--) { ret = __posix_fadvise64(fd, offset, length, advice); if (ret) { fprintf(stderr, "%s: fadvise() failed: %s\n", progname, strerror(errno)); exit(1); } } close(fd); exit(0); } --FCuugMFkClbJLl1L Content-Type: text/x-chdr; charset=us-ascii Content-Disposition: attachment; filename="fadvise.h" #include #include #ifndef __NR_fadvise64 #if defined (__i386__) #define __NR_fadvise64 250 #elif defined(__powerpc__) #define __NR_fadvise64 233 #elif defined(__ia64__) #define __NR_fadvise64 1234 #elif defined(__x86_64__) #define __NR_fadvise64 221 #endif #endif #ifndef LINUX_FADV_ASYNC_WRITE #define LINUX_FADV_ASYNC_WRITE 32 #endif #ifndef LINUX_FADV_WRITE_WAIT #define LINUX_FADV_WRITE_WAIT 33 #endif #ifndef __x86_64__ _syscall5(int,fadvise64, int,fd, long,offset_lo, long,offset_hi, size_t,len, int,advice) #endif /* Works by luck on ppc32, fails on ppc64 */ #if defined(__i386__) int __posix_fadvise(int fd, off_t offset, size_t len, int advice) { return fadvise64(fd, offset, 0, len, advice); } int __posix_fadvise64(int fd, loff_t offset, size_t len, int advice) { return fadvise64(fd, offset, offset >> 32, len, advice); } #elif defined(__powerpc64__) int __posix_fadvise(int fd, off_t offset, size_t len, int advice) { return fadvise64(fd, offset, len, advice); } int __posix_fadvise64(int fd, loff_t offset, size_t len, int advice) { return fadvise64(fd, offset, len, advice); } #elif defined(__powerpc__) /* * long longs are passed in an odd even register pair on ppc32 so * we need to pad before offset * * Note also the glibc syscall() function for ppc has been broken for * 6 argument syscalls until recently (~2.3.1 CVS) */ #define ppc_fadvise64(fd, offset_hi, offset_lo, len, advice) \ syscall(__NR_fadvise64, fd, 0, offset_hi, offset_lo, len, advice) int __posix_fadvise(int fd, off_t offset, size_t len, int advice) { return ppc_fadvise64(fd, 0, offset, len, advice); } /* big endian, akpm. */ int __posix_fadvise64(int fd, loff_t offset, size_t len, int advice) { return ppc_fadvise64(fd, (unsigned int)(offset >> 32), (unsigned int)(offset & 0xffffffff), len, advice); } #elif defined(__ia64__) int __posix_fadvise(int fd, off_t offset, size_t len, int advice) { return fadvise64(fd, offset, len, advice); } int __posix_fadvise64(int fd, loff_t offset, size_t len, int advice) { return fadvise64(fd, offset, len, advice); } #elif defined(__x86_64__) int __posix_fadvise(int fd, off_t offset, size_t len, int advice) { return -1; } int __posix_fadvise64(int fd, loff_t offset, size_t len, int advice) { return syscall(__NR_fadvise64, fd, offset, len, advice); } #endif --FCuugMFkClbJLl1L--