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SuperMe
n00b
Joined: 30 May 2005
Posts: 25
Location: London, UK
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 Posted: Sun Jan 28, 2007 1:17 am Post subject: mysql Memory Usage |
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I have a local Gentoo server which I use as a playground. I am developing a new website and so am having a look at apache2 and gallery2 using a mysql database. The mysql demon seems to be using a lot more memory than anything else running on my system. This isn't a problem as I have 2GB however I am curious why it's using so much considering it's doing so little. Any ideas?
| Code: | top - 02:06:32 up 7:45, 2 users, load average: 0.00, 0.00, 0.00
Tasks: 64 total, 2 running, 61 sleeping, 1 stopped, 0 zombie
Cpu(s): 0.0% us, 0.0% sy, 0.0% ni, 100.0% id, 0.0% wa, 0.0% hi, 0.0% si
Mem: 2025900k total, 1309148k used, 716752k free, 281108k buffers
Swap: 8016416k total, 0k used, 8016416k free, 468252k cached
PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4854 mysql 18 0 144m 28m 3924 S 0 1.5 0:00.06 mysqld
9222 postgres 16 0 41896 6820 6192 S 0 0.3 0:00.08 postmaster
5012 root 15 0 66060 5428 2528 S 0 0.3 0:00.01 apache2
5077 monotone 19 0 19480 5212 3996 S 0 0.3 0:00.05 mtn
5081 nick 18 0 66060 3840 928 S 0 0.2 0:00.00 apache2
5082 nick 18 0 66060 3840 928 S 0 0.2 0:00.00 apache2
5083 nick 21 0 66060 3840 928 S 0 0.2 0:00.00 apache2
5084 nick 20 0 66060 3840 928 S 0 0.2 0:00.00 apache2
5085 nick 20 0 66060 3840 928 S 0 0.2 0:00.00 apache2
5497 root 16 0 21232 2300 1792 S 0 0.1 0:00.04 sshd
8767 root 16 0 21228 2296 1792 S 0 0.1 0:00.04 sshd
5154 root 20 0 27484 2216 1320 S 0 0.1 0:00.00 smbd
8770 nick 16 0 10464 1832 1348 S 0 0.1 0:00.01 bash
5500 nick 16 0 10468 1828 1340 S 0 0.1 0:00.00 bash
9229 postgres 15 0 23868 1652 508 S 0 0.1 0:00.00 postmaster
5499 nick 15 0 21384 1504 968 S 0 0.1 0:02.14 sshd
8769 nick 16 0 21380 1488 968 R 0 0.1 0:00.13 sshd
9227 postgres 16 0 41896 1332 672 S 0 0.1 0:00.00 postmaster
9682 nick 16 0 10536 1268 940 R 0 0.1 0:00.00 top
4944 root 16 0 18672 1184 752 S 0 0.1 0:00.00 sshd
5164 root 15 0 10976 1164 800 S 0 0.1 0:00.52 nmbd
5158 root 20 0 27484 1136 240 S 0 0.1 0:00.00 smbd
9228 postgres 16 0 24372 1108 476 S 0 0.1 0:00.00 postmaster
8775 nick 16 0 5048 808 636 T 0 0.0 0:00.00 pg
5233 root 16 0 9012 720 572 S 0 0.0 0:00.00 cron
5321 root 17 0 3672 684 572 S 0 0.0 0:00.00 agetty
5323 root 17 0 3672 684 572 S 0 0.0 0:00.00 agetty
5318 root 16 0 3672 680 572 S 0 0.0 0:00.00 agetty
5320 root 16 0 3672 680 572 S 0 0.0 0:00.00 agetty
5317 root 17 0 3668 676 572 S 0 0.0 0:00.00 agetty
5319 root 17 0 3668 676 572 S 0 0.0 0:00.00 agetty
1121 root 21 -4 7056 624 340 S 0 0.0 0:00.28 udevd
4296 root 15 0 4936 620 392 S 0 0.0 0:00.00 syslog-ng
1 root 16 0 2604 568 484 S 0 0.0 0:00.47 init |
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drescherjm
Advocate
Joined: 05 Jun 2004
Posts: 2790
Location: Pittsburgh, PA, USA
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| Posted: Sun Jan 28, 2007 5:08 am Post subject: |
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If I read this correctly mysql is using 144MB which is small in my opinion.
Now if you are talking about the system memory usage this is actually a very good feature of linux. As linux will use almost all of your unused memory for disk cache. When an application requests some the disk cache will shrink.
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My gentoo overlay
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SuperMe
n00b
Joined: 30 May 2005
Posts: 25
Location: London, UK
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| Posted: Mon Jan 29, 2007 10:31 am Post subject: |
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| Thanks. To me 144MB seemed a lot considering it's not doing anything. I just wanted to check if this was normal or if I had some sort of problem. |
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lluthor
n00b
Joined: 28 Jan 2007
Posts: 4
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| Posted: Mon Jan 29, 2007 10:55 am Post subject: Re: mysql Memory Usage |
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| SuperMe wrote: | PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND
4854 mysql 18 0 144m 28m 3924 S 0 1.5 0:00.06 mysqld
[/code] |
You are reading it incorrectly.
mysql is using 144MB of virtual memory (i.e. address space), this is likely due mmap()ing some data files. This is good, since the kernel can freely allocate and deallocate this as needed, even for dirty pages, since they can be written straight to disk whenever, and clean pages can simply be dropped and page-faulted back in when needed.
Out of this 144MB, mysql is actually only using 28M of dirty memory (memory that cannot simply be dropped by the kernel), and even this can be paged if needed.
The rest of the 144MB, mysql is using ~4MB of clean memory (this is likely the binaries and libraries of mysql) and this can be dropped and faulted as well, and the libraries (and the read-only portions of the binaries) are also shareable like glibc so they consume a constant amount no matter how many processes use them. |
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