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Re: [PATCH] aarch64: Add tunable glibc.memset.dc_zva_threshold
- From: Szabolcs Nagy <Szabolcs dot Nagy at arm dot com>
- To: Feng Xue OS <fxue at os dot amperecomputing dot com>, "libc-alpha at sourceware dot org" <libc-alpha at sourceware dot org>
- Cc: nd <nd at arm dot com>
- Date: Fri, 26 Jul 2019 15:17:39 +0000
- Subject: Re: [PATCH] aarch64: Add tunable glibc.memset.dc_zva_threshold
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On 26/07/2019 12:58, Feng Xue OS wrote:
> This patch is composed to add a tunable 'glibc.memset.dc_zva_threshold'
> to control using DC ZVA in memset or not. Only when memset size exceeds
> this threshold, DC ZVA will be used.
>
> The background is that DC ZVA does not always outperform normal
> memory-store zeroing, especially when there are multiple processes/threads
> contending for memory/cache.
adding a threshold to memset_emag is fine, but
i'm not yet convinced that a tunable threshold
is useful enough.
is it expected that different workloads require
different setting? is this effect significant?