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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1qqgXm-00CzJT-7I; Wed, 11 Oct 2023 21:15:02 +0000 Date: Wed, 11 Oct 2023 22:15:02 +0100 From: Matthew Wilcox To: Gregory Price Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-cxl@vger.kernel.org, akpm@linux-foundation.org, sthanneeru@micron.com, ying.huang@intel.com, gregory.price@memverge.com Subject: Re: [RFC PATCH v2 0/3] mm: mempolicy: Multi-tier weighted interleaving Message-ID: References: <20231009204259.875232-1-gregory.price@memverge.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20231009204259.875232-1-gregory.price@memverge.com> X-Rspamd-Queue-Id: 22EE0180004 X-Rspam-User: X-Rspamd-Server: rspam04 X-Stat-Signature: 6w8hnptgm8yt7day8htsytkj6ieqmtbu X-HE-Tag: 1697058905-501265 X-HE-Meta: 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 mCj+gGIJ yc7o7LL2BgEWVVu0/y/HlGzIOfsN1FEyPSSTUucd5pyW71azZBkig0BpKCrpoRWN227Pecf/kFkrPPZAT09EbtdhdSY9Derovb8gS+2VHdcumKL5NT8guhtlJ23w7KD2hWajAxyhWMN8RJdbz0BzrbCnHCoDmjkCFzL52RAGYhy5wffe573AOmNfNXq80KeT/RMl43AFeJC2VXxVhATQVcjlmL3TG2flVYKfN1UKBPONNp+Y= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, Oct 09, 2023 at 04:42:56PM -0400, Gregory Price wrote: > == Mutex to Semaphore change: > > The memory tiering subsystem is extended in this patch set to have > externally available information (weights), and therefore additional > controls need to be added to ensure values are not changed (or tiers > changed/added/removed) during various calculations. > > Since it is expected that many threads will be accessing this data > during allocations, a mutex is not appropriate. > > Since write-updates (weight changes, hotplug events) are rare events, > a simple rw semaphore is sufficient. Given how you're using it, wouldn't the existing RCU mechanism be better than converting this to an rwsem?