| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Vladimir Churyukin <vladimir(at)churyukin(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Bypassing shared_buffers |
| Date: | 2023-06-15 02:28:24 |
| Message-ID: | CA+hUKGJNsXGjhsoQCKtFs32W6eLH=P7aWPcHqmq_VV4qxr=2KA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jun 15, 2023 at 1:37 PM Vladimir Churyukin
<vladimir(at)churyukin(dot)com> wrote:
> Ok, got it, thanks.
> Is there any alternative approach to measuring the performance as if the cache was empty?
There are two levels of cache. If you're on Linux you can ask it to
drop its caches by writing certain values to /proc/sys/vm/drop_caches.
For PostgreSQL's own buffer pool, it would be nice if someone would
extend the pg_prewarm extension to have a similar 'unwarm' operation,
for testing like that. But one thing you can do is just restart the
database cluster, or use pg_prewarm to fill its buffer pool up with
other stuff (and thus kick out the stuff you didn't want in there).
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