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Date: Wed, 4 Mar 2009 19:57:02 +0800 From: Wu Fengguang <fengguang.wu@...el.com> To: Markus <M4rkusXXL@....de> Cc: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, linux-mm@...ck.org Subject: Re: drop_caches ... On Wed, Mar 04, 2009 at 01:29:40PM +0200, Markus wrote: > > > > The memory mapped pages won't be dropped in this way. > > > > "cat /proc/meminfo" will show you the number of mapped pages. > > > > > > # sync ; echo 3 > /proc/sys/vm/drop_caches ; free -m ; > cat /proc/meminfo > > > total used free shared buffers > > > cached > > > Mem: 3950 3262 688 0 0 > > > 359 > > > -/+ buffers/cache: 2902 1047 > > > Swap: 5890 1509 4381 > > > MemTotal: 4045500 kB > > > MemFree: 705180 kB > > > Buffers: 508 kB > > > Cached: 367748 kB > > > SwapCached: 880744 kB > > > Active: 1555032 kB > > > Inactive: 1634868 kB > > > Active(anon): 1527100 kB > > > Inactive(anon): 1607328 kB > > > Active(file): 27932 kB > > > Inactive(file): 27540 kB > > > Unevictable: 816 kB > > > Mlocked: 0 kB > > > SwapTotal: 6032344 kB > > > SwapFree: 4486496 kB > > > Dirty: 0 kB > > > Writeback: 0 kB > > > AnonPages: 2378112 kB > > > Mapped: 52196 kB > > > Slab: 65640 kB > > > SReclaimable: 46192 kB > > > SUnreclaim: 19448 kB > > > PageTables: 28200 kB > > > NFS_Unstable: 0 kB > > > Bounce: 0 kB > > > WritebackTmp: 0 kB > > > CommitLimit: 8055092 kB > > > Committed_AS: 4915636 kB > > > VmallocTotal: 34359738367 kB > > > VmallocUsed: 44580 kB > > > VmallocChunk: 34359677239 kB > > > DirectMap4k: 3182528 kB > > > DirectMap2M: 1011712 kB > > > > > > The cached reduced to 359 MB (after the dropping). > > > I dont know where to read the "number of mapped pages". > > > "Mapped" is about 51 MB. > > > > Does your tmpfs store lots of files? > > Dont think so: > > # df -h > Filesystem Size Used Avail Use% Mounted on > /dev/md6 14G 8.2G 5.6G 60% / > udev 10M 304K 9.8M 3% /dev > cachedir 4.0M 100K 4.0M 3% /lib64/splash/cache > /dev/md4 19G 15G 3.1G 83% /home > /dev/md3 8.3G 4.5G 3.9G 55% /usr/portage > shm 2.0G 0 2.0G 0% /dev/shm > /dev/md1 99M 19M 76M 20% /boot > > # mount > /dev/md6 on / type ext3 (rw,noatime,nodiratime,barrier=0) > /proc on /proc type proc (rw,noexec,nosuid,noatime,nodiratime) > sysfs on /sys type sysfs (rw,nosuid,nodev,noexec) > udev on /dev type tmpfs (rw,nosuid,size=10240k,mode=755) > devpts on /dev/pts type devpts (rw,nosuid,noexec,gid=5,mode=620) > cachedir on /lib64/splash/cache type tmpfs (rw,size=4096k,mode=644) > /dev/md4 on /home type ext3 (rw,noatime,nodiratime,barrier=0) > /dev/md3 on /usr/portage type ext4 (rw,noatime,nodiratime,barrier=0) > shm on /dev/shm type tmpfs (rw,noexec,nosuid,nodev) > usbfs on /proc/bus/usb type usbfs > (rw,noexec,nosuid,devmode=0664,devgid=85) > automount(pid6507) on /mnt/.autofs/misc type autofs > (rw,fd=4,pgrp=6507,minproto=2,maxproto=4) > automount(pid6521) on /mnt/.autofs/usb type autofs > (rw,fd=4,pgrp=6521,minproto=2,maxproto=4) > /dev/md1 on /boot type ext2 (rw,noatime,nodiratime) > > I dont know what exactly all that memory is used for. It varies from > about 300 MB to up to one GB. > Tell me where to look and I will! So you don't have lots of mapped pages(Mapped=51M) or tmpfs files. It's strange to me that there are so many undroppable cached pages(Cached=359M), and most of them lie out of the LRU queue(Active+Inactive file=53M)... Anyone have better clues on these 'hidden' pages? Thanks, Fengguang -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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