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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?RNb8s4+hP2D6FPFhbWvo4Z/bV0d0hGmbjP9s/rI3Kb+rhJkaJJu4luYQY3TT?= =?us-ascii?Q?RyU5xAG5fW5XvILBS0BRb23msocoXrQpnOU4JPnj5LQAVxTiIFq85DI06eJy?= =?us-ascii?Q?48r+TTRha1U8W4LVbBGFcJKMKGjjlTpWQBpQEuBkZapK9NLwV6icZjuee3dk?= =?us-ascii?Q?HaJqkFphHxrSFo/fRlKNulsltxl132JrFS1iroRrM38KbobxHTfHdT3LW11z?= =?us-ascii?Q?zB/OpXhEsO6O4YBrvoW4hSFeEhCnmUlh5sNM2pjYp9vTZPXJ9Eo/DDLyaoVF?= =?us-ascii?Q?CobX/Bnuvj3Kgaq+svvYUi292W/FIhNnWMyESZSWMTaSg4p/c5bOJWUGceYr?= =?us-ascii?Q?3rngmD3GYimGmV8Wj9DFJPqZXvz/6JQpeavxY7rmf3Y9bHgvJhHWuLwy+/59?= =?us-ascii?Q?vTemEb8vztVn/myPcnsArrPrtobT+JV0me+Nu/isO8E/4cCHdKVX3GvBX6zi?= =?us-ascii?Q?R6QoL8fdRwPcPFrQljZr/uD3qWVTNJhUowA1ADAvgqwj6IhZDYj8bYkE2/4k?= =?us-ascii?Q?k/tfvbTzhNFGwNeadPrkWgN6BKrnsnvlzIfKyfltu+bq7QaoJsA2tuCkyxjL?= =?us-ascii?Q?jMqV1dFSaB3DYRicjRg3fll1ThINJui1zbIuTdhNWPt0xPUOHg+n2fw5i7p0?= =?us-ascii?Q?qRGGCvqXbmxJ3PWak59zYfcTguNidI+lwP8p16YJHLgYC30xMCuyAeBYQr1V?= =?us-ascii?Q?dCbhTatnGosxAJQsPrjIhnRfbHZXOthFyeYmEFvyJZvoakL/ezeY55qE0NtK?= =?us-ascii?Q?+eaEwdasqgjUFkgeULK1ibCW8XfMGI1dNDFEzjg+1jRcP3N1FnNm0AqDxYdG?= =?us-ascii?Q?0WUAv/AlAC9EfbpVxqld9As2causvRWLYa1zKmAHRx99cN22rOZUpQpBQ7T1?= =?us-ascii?Q?TRInqTPuSk4zp2HY3HaVwSDYpbhU7gQd5y0wEVgva3IuzUpKKBZX1FHubyhp?= =?us-ascii?Q?keFXWa/Mg0odaUG96z6C52GRKNxPfgJKUF9BBEXin0ALSoFEnvO14AQI0qXL?= =?us-ascii?Q?qX7scbyEe3zSvHLLpm2w9xK6HiYaBt1vNmz8VgzU3i3EPifAdYDm4WqIBxvL?= =?us-ascii?Q?ot+dLmDQ8k3KJagYZY9UtYxcM1lmfEy2oZfpSxU3ky1Z0d/pY+ASq4YGyvjI?= =?us-ascii?Q?lZtM2HGiA2zJpLoEonnNbYWi+tUvWdA5zEu+Do2xAFjHX4AYfNMjC/SsNvt4?= =?us-ascii?Q?YTTHqm4JRYiQuOmnEaPszO4H7n+tkHtsyw6qz+GV7/tuykR7itkTKr4ujdMn?= =?us-ascii?Q?xq7BWE7/HpTosFKDjpw6abQwRcHBJMO5jELBnarKsna9VruOfNgjtkVv55K+?= =?us-ascii?Q?71u8Tx58NPS2rZqDaZ+DWwDNlhCj7EsIz9wvTVohPUV+fmIVxqQNlGHQK8iL?= =?us-ascii?Q?4gSBKOA8/7dM7LXTmPv3pO6w+UYhXc1pk2b5kCbISSJUxQBe/rSNHCkBG0C8?= =?us-ascii?Q?nEKo4rtZ2EQJE0XHSTW2AC8MC/xGyBSCEMH+afmzmJdiUl1AHx22QvZfbNAE?= =?us-ascii?Q?P1Dis0F7LdrAAkFk5qyFndpaUYduWiin7wEdH5EP/WJueo7L+ZaJb1d6/VDd?= =?us-ascii?Q?wCUq+TINiVlP8HJN7GqonAqdTZIq3CzR7ynRFepv2zISDUHIV52NoCVg6eKK?= =?us-ascii?Q?uA=3D=3D?= X-OriginatorOrg: memverge.com X-MS-Exchange-CrossTenant-Network-Message-Id: 08768328-a658-4da7-5919-08db353c6f17 X-MS-Exchange-CrossTenant-AuthSource: SJ0PR17MB5512.namprd17.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 04 Apr 2023 18:43:08.3792 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 5c90cb59-37e7-4c81-9c07-00473d5fb682 X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: YpEIX1CZ82jMrMFEdK6yDh1kfIzFBPVY96fSGVrdGpXZU6/zcm/XdkT5yi7+4DaJKhTYWx2qnzJvx6cJe8PYmXaveq+eGeXrbvXJ0OcUPts= X-MS-Exchange-Transport-CrossTenantHeadersStamped: SJ0PR17MB4728 Precedence: bulk List-ID: X-Mailing-List: linux-cxl@vger.kernel.org On Tue, Apr 04, 2023 at 05:58:05PM +0000, Adam Manzanares wrote: > On Tue, Apr 04, 2023 at 11:31:08AM +0300, Mike Rapoport wrote: > > > > The point of zswap IIUC is to have small and fast swap device and > > compression is required to better utilize DRAM capacity at expense of CPU > > time. > > > > Presuming CXL memory will have larger capacity than DRAM, why not skip the > > compression and use CXL as a swap device directly? > > I like to shy away from saying CXL memory should be used for swap. I see a > swap device as storing pages in a manner that is no longer directly addressable > by the cpu. > > Migrating pages to a CXL device is a reasonable approach and I believe we > have the ability to do this in the page reclaim code. > The argument is "why do you need swap if memory itself is elastic", and I think there are open questions about how performant using large amounts of high-latency memory is. Think 1us-1.5us+ cross-rack attached memory. Does it make sense to use that as CPU-addressible and migrate it on first use? Isn't that just swap with more steps? What happens if we just use it as swap, is the performance all that different? I think there's a reasonable argument for exploring the idea at the higher ends of the latency spectrum. And the simplicity of using an existing system (swap) to implement a form of proto-tiering is rather attractive in my opinion. ~Gregory