drop duplicate buffers in OS

From: KONDO Mitsumasa <kondo(dot)mitsumasa(at)lab(dot)ntt(dot)co(dot)jp>
To: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: drop duplicate buffers in OS
Date: 2014-01-15 06:53:07
Message-ID: 52D63053.7000003@lab.ntt.co.jp
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I create patch that can drop duplicate buffers in OS using usage_count
alogorithm. I have developed this patch since last summer. This feature seems to
be discussed in hot topic, so I submit it more faster than my schedule.

When usage_count is high in shared_buffers, they are hard to drop from
shared_buffers. However, these buffers wasn't required in file cache. Because
they aren't accessed by postgres(postgres access to shared_buffers).
So I create algorithm that dropping file cache which is high usage_count in
shared_buffers and is clean state in OS. If file cache are clean state in OS, and
executing posix_fadvice DONTNEED, it can only free in file cache without writing
physical disk. This algorithm will solve double-buffered situation problem and
can use memory more efficiently.

I am testing DBT-2 benchmark now...

Mitsumasa KONDO
NTT Open Source Software Center

Attachment Content-Type Size
drop_duplicate_buffers_v4.patch text/x-diff 13.5 KB


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