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Re: very poor performance of opening tables
Posted by: J G
Date: September 25, 2005 11:16AM

Jay Pipes wrote:
> To the best of my knowledge, SIGUSR2 is used to
> resume a suspended thread. [...]

Thank you for your post. That's very important for me, now I know I find another hints.

This truss has been done when table_cache=0 so number of opened file descriptors was very low. I've discovered that in my situation table_cache hasn't any noticable effect on performance, because there are so much tables. The less table_cache the better for me, because I've less RAM usage.

I had also idea that my problems were caused by poor symlink performance on FreeBSD, so I've created a small ramdisk as MySQL datadir with links to my 20.000 databases, but performance is the same as on normal hard drive, so readlink() performance on FreeBSD is quiet good. My ramdisk has been mounted on UFS2 with async and noatime.

I've also tried native freebsd threads (KSE) rather than linux_threads. I've noticable performance hit, maybe ~100 more queries/s, but my problem with tables opening still exist. As I said I am expecting about 1600q/s on this hardware... So now I'm sure my problem is not releated to emulation of linux_threads.

I think I will try to install Gentoo (it's like *BSD :), but I need to have same second server for tests. Maybe next week.

What do you recommend, RAID0 with 4 disks or my present solution: MySQL datadir in the ramdisk, and there a lots of symlinks to 20.000 databases located on other four hard drives without raid ?



Edited 2 time(s). Last edit at 09/25/2005 11:21AM by J G.

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Re: very poor performance of opening tables
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