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List:       openjdk-hotspot-runtime-dev
Subject:    Re: RFR: JDK-8303051: Stop saving 5 chunks in each ChunkPool [v4]
From:       Johan =?UTF-8?B?U2rDtmxlbg==?= <jsjolen () openjdk ! org>
Date:       2023-02-27 11:08:16
Message-ID: BWMGxqgwa6PErT78IUZvK-_1n70hcwssIjgbFViXUwU=.fa0148b3-4545-4d2e-bffd-b4fedd46491d () github ! com
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On Thu, 23 Feb 2023 10:51:32 GMT, Johan Sjölen <jsjolen@openjdk.org> wrote:

> > In the 4 pre-defined ChunkPools the pruner save 5 chunks for re-use later in the \
> > program. The pruner runs every 5 seconds and saves the first 5 chunks that were \
> > last freed and put into the pool. In other words: The lifetime of these 5 chunks \
> > are indeterminate, we don't know when these will be freed. This is a problem, \
> > because these chunks are allocated with os::malloc(). We might be clobbering our \
> > underlying malloc's capacity to shrink its own arena sizes because of the \
> > placement of these chunks, and it would be very difficult for us to know whether \
> > this is the case. 
> > I suggest that we stop saving these 4*5 chunks and always remove all free chunks \
> > when cleaning the pools. 
> > Passes Arena gtests, running tier1.
> 
> Johan Sjölen has updated the pull request incrementally with one additional commit \
> since the last revision: 
> Forgot to set _first

No protests have arrived, integrating this!

-------------

PR: https://git.openjdk.org/jdk/pull/12710


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