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From: Nazir Bilal Yavuz <byavuz81@gmail.com>
To: Melanie Plageman <melanieplageman@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Andres Freund <andres@anarazel.de>
Subject: Re: Checkpointer write combining
Date: Tue, 9 Sep 2025 16:27:47 +0300
Message-ID: <CAN55FZ3FOv+ubp4yyFKt=Rr+ceM0tfXRDVr6nKgqSyWXh8G8Gg@mail.gmail.com> (raw)
In-Reply-To: <CAAKRu_bQWv5hJH0ncbGw8BEufAxdwMw4KY0KYuYLaw6KA=fpCA@mail.gmail.com>
References: <CAAKRu_bcWRvRwZUop_d9vzF9nHAiT+-uPzkJ=S3ShZ1GqeAYOw@mail.gmail.com>
	<CAAKRu_bQWv5hJH0ncbGw8BEufAxdwMw4KY0KYuYLaw6KA=fpCA@mail.gmail.com>

Hi,

Thank you for working on this!

On Tue, 9 Sept 2025 at 02:44, Melanie Plageman
<melanieplageman@gmail.com> wrote:
>
> On Tue, Sep 2, 2025 at 5:10 PM Melanie Plageman
> <melanieplageman@gmail.com> wrote:
> >
> > The attached patchset implements checkpointer write combining -- which
> > makes immediate checkpoints at least 20% faster in my tests.
> > Checkpointer achieves higher write throughput and higher write IOPs
> > with the patch.

I did the same benchmark you did and I found it is %50 faster (16
seconds to 8 seconds).

From 053dd9d15416d76ce4b95044d848f51ba13a2d20 Mon Sep 17 00:00:00 2001
From: Melanie Plageman <melanieplageman@gmail.com>
Date: Tue, 2 Sep 2025 11:00:44 -0400
Subject: [PATCH v2 1/9] Refactor goto into for loop in GetVictimBuffer()

@@ -731,6 +741,13 @@ StrategyRejectBuffer(BufferAccessStrategy
strategy, BufferDesc *buf, bool from_r
         strategy->buffers[strategy->current] != BufferDescriptorGetBuffer(buf))
         return false;

+    buf_state = LockBufHdr(buf);
+    lsn = BufferGetLSN(buf);
+    UnlockBufHdr(buf, buf_state);
+
+    if (!XLogNeedsFlush(lsn))
+        return true;

I think this should return false.

I am planning to review the other patches later and this is for the
first patch only.

--
Regards,
Nazir Bilal Yavuz
Microsoft

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