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Tue, 03 Mar 2026 12:27:11 -0800 (PST) Date: Tue, 3 Mar 2026 15:27:00 -0500 From: Peter Xu To: =?utf-8?Q?Marc-Andr=C3=A9?= Lureau Cc: David Hildenbrand , qemu-devel@nongnu.org, Ben Chaney , "Michael S. Tsirkin" , =?utf-8?Q?C=C3=A9dric?= Le Goater , Paolo Bonzini , Alex Williamson , Fabiano Rosas , Philippe =?utf-8?Q?Mathieu-Daud=C3=A9?= , kvm@vger.kernel.org, Mark Kanda Subject: Re: [PATCH v3 09/15] system/ram-discard-manager: implement replay via is_populated iteration Message-ID: References: <20260226140001.3622334-1-marcandre.lureau@redhat.com> <20260226140001.3622334-10-marcandre.lureau@redhat.com> <99b0ab59-c1dc-4d23-addc-7bf4b87bfa03@kernel.org> Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: On Tue, Mar 03, 2026 at 11:47:52AM +0100, Marc-André Lureau wrote: > We can still iterate with 2M granularity after this patch. However, it > may be less effective than iterating using find_next_bit(). Whether > this is noticeable remains to be seen. IIUC when in extreme scattered cases the results should be similar, say, when the bitmap (2M for each bit) is 10101010....10101b. OTOH the worst case scenario here is when e.g. the whole region is fully populated. So.. if we have any concern, maybe we could run a VFIO population test on non-CoCo, before or after this patch, having the whole region requested available (so a bitmap with 111111111....111111b). Thanks, -- Peter Xu