From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp-fw-80006.amazon.com (smtp-fw-80006.amazon.com [99.78.197.217]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C828453E23; Thu, 27 Mar 2025 17:28:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=99.78.197.217 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743096526; cv=none; b=uEhNDDoc6sOWCnF1BPCNErgZ4y12+0sBsDswrc9SEQiFoFcpiXiI+96j7+K1EAVtMGcF4P+EMriz37LT18j5luJRw46BZlZoad9sdS/c6Wd0hZenPADzJgDtQEjOtVu4/85G5nsSeXzm89z6+5ZHU5CmjKsvfGujM9EEHOzLfls= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1743096526; c=relaxed/simple; bh=m/KjN2TK9DC6QJRxDx0XiqFQ1tXNoM6xFIpl8JXP8yc=; h=From:To:CC:Subject:In-Reply-To:References:Date:Message-ID: MIME-Version:Content-Type; b=EBYid3smeZ0u9jTEm00rNxdK0zAcAZqSx26lzcNV5SqpuNEeLTNTnirbgllgJJAHXmLbb9u3Am09Oy8QXexhsQejxMLSHkWM8PJwUFK8Gdr7TKAIQ9z3NdK+9Z3hCKCwDoKR5eEzdEN2O6n0eEwTeOUKSRw8T9zb+/PyHdfEcCY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.de; spf=pass smtp.mailfrom=amazon.de; dkim=pass (1024-bit key) header.d=amazon.de header.i=@amazon.de header.b=P574VVFL; arc=none smtp.client-ip=99.78.197.217 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amazon.de Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=amazon.de Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amazon.de header.i=@amazon.de header.b="P574VVFL" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amazon.de; i=@amazon.de; q=dns/txt; s=amazon201209; t=1743096525; x=1774632525; h=from:to:cc:subject:in-reply-to:references:date: message-id:mime-version; bh=xSuF/YbxgWCWLj2Pm2m2fnuZ8qcDIDPazYI7pzm5ruM=; b=P574VVFLLihRrLrYqkhjeg1fhqYasvZyAx97Q4qwAa1XE2jIQT9Zwshf 6mKdA22g2NKLos5QL0rXhOpLclFyzO/xDMiDfwox+bpzIVfdmZkTNs80w 3cMtr+ynbhhJIRCjBV7zDlAQvs90tKfkCKmy8gzTgXwvetM6TsyV/UWjp o=; X-IronPort-AV: E=Sophos;i="6.14,281,1736812800"; d="scan'208";a="35764312" Received: from pdx4-co-svc-p1-lb2-vlan3.amazon.com (HELO smtpout.prod.us-west-2.prod.farcaster.email.amazon.dev) ([10.25.36.214]) by smtp-border-fw-80006.pdx80.corp.amazon.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 27 Mar 2025 17:28:43 +0000 Received: from EX19MTAUWC001.ant.amazon.com [10.0.38.20:63978] by smtpin.naws.us-west-2.prod.farcaster.email.amazon.dev [10.0.62.254:2525] with esmtp (Farcaster) id 5fc1b816-d2cf-4e8d-a1ff-9170cc525ffa; Thu, 27 Mar 2025 17:28:42 +0000 (UTC) X-Farcaster-Flow-ID: 5fc1b816-d2cf-4e8d-a1ff-9170cc525ffa Received: from EX19D020UWC001.ant.amazon.com (10.13.138.157) by EX19MTAUWC001.ant.amazon.com (10.250.64.174) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Thu, 27 Mar 2025 17:28:41 +0000 Received: from EX19MTAUWA002.ant.amazon.com (10.250.64.202) by EX19D020UWC001.ant.amazon.com (10.13.138.157) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14; Thu, 27 Mar 2025 17:28:41 +0000 Received: from email-imr-corp-prod-pdx-all-2c-c4413280.us-west-2.amazon.com (10.25.36.210) by mail-relay.amazon.com (10.250.64.203) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA) id 15.2.1544.14 via Frontend Transport; Thu, 27 Mar 2025 17:28:41 +0000 Received: from dev-dsk-ptyadav-1c-43206220.eu-west-1.amazon.com (dev-dsk-ptyadav-1c-43206220.eu-west-1.amazon.com [172.19.91.144]) by email-imr-corp-prod-pdx-all-2c-c4413280.us-west-2.amazon.com (Postfix) with ESMTP id 3538AA04D5; Thu, 27 Mar 2025 17:28:41 +0000 (UTC) Received: by dev-dsk-ptyadav-1c-43206220.eu-west-1.amazon.com (Postfix, from userid 23027615) id BF36651B7; Thu, 27 Mar 2025 17:28:40 +0000 (UTC) From: Pratyush Yadav To: Jason Gunthorpe CC: Changyuan Lyu , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , , Subject: Re: [PATCH v5 09/16] kexec: enable KHO support for memory preservation In-Reply-To: References: <20250320015551.2157511-1-changyuanl@google.com> <20250320015551.2157511-10-changyuanl@google.com> Date: Thu, 27 Mar 2025 17:28:40 +0000 Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain On Thu, Mar 27 2025, Jason Gunthorpe wrote: > On Thu, Mar 27, 2025 at 10:03:17AM +0000, Pratyush Yadav wrote: > >> Of course, with the current linked list structure, this cannot work. But >> I don't see why we need to have it. I think having a page-table like >> structure would be better -- only instead of having PTEs at the lowest >> levels, you have the bitmap. > > Yes, but there is a trade off here of what I could write in 30 mins > and what is maximally possible :) The xarray is providing a page table > implementation in a library form. > > I think this whole thing can be optimized, especially the > memblock_reserve side, but the idea here is to get started and once we > have some data on what the actual preservation workload is then > someone can optimize this. > > Otherwise we are going to be spending months just polishing this one > patch without any actual data on where the performance issues and hot > spots actually are. The memblock_reserve side we can optimize later, I agree. But the memory preservation format is ABI and I think that is worth spending a little more time on. And I don't think it should be that much more complex than the current format. I want to hack around with it, so I'll give it a try over the next few days and see what I can come up with. -- Regards, Pratyush Yadav