Re: filesystemio_options 12.2

On Fri, 2024-11-08 at 22:31 +0100, pier paolo Bruno wrote:
> Hi, i have  single instance database on linux , ext4 . it is a 12.2,
> with patchset April 2020 on top.
> I have performance problems.
> The first thing i see is that the server is swapping. It is a vm with
> 23gb of ram and an instance with 12g sga.
> if i do vmstat -m or free .m i see that buffer/cache is 14gb .
> I have also seen that filesystemio_options is set to none.
> Is that correct ? would not be better to set it to set_all and try to
> not rely on filesystem cache as it was on older releases ?
> I tried to check support and documentation, i still see that parameter
> is till there but i find notes for the most on older releases ( 9..
> 10.. .11 ) and so i asked myself if it was something till to use .
> Thanks
> Pier Paolo
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>
>

I don't usually go over 50% of RAM with SGA. Second, you really do need filesystemio_options set to either SETALL or DIRECT. Direct I/O will bypass OS buffering and save some memory. Last, but definitely not least, Ext4 is the wrong FS type. Namely, Ext4 cannot write in parallel. It can only process 1 I/O request at a time. I would recommend XFS to house data files. Also, you need huge pages configured to save memory. Page tables will be a bit smaller with 2MB page size than with 4KB page size.

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