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X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: IA7WCHcyPPGNHpCdxxDOQI8hBGbL1PivfCZAWek/NrdZgBur0QKRv+eYjDY2Ht0Mt4G6cX3KIBXkUFcc+HRbrTzCJBo9Na8dgKQnd3XaHKE4nrAOGtjdJrSx/YEmF5ojS73oXsmaDLN/Xh5aeqp1A1+a0TILzJjNpDPdWJrluPu2dXWVzZ8xrlRJVxrJQZkqOZoo83PGS1ZyRSbzQQl+ar3LP3pzD+y4pfK4DC+sRMjCgRlCfCGJqfGwCbwsFW+YFsDizaiyj/D3ytBTPLpSEOr23MIokjijknDqLVMKSt7vMRsvmPphaenniE0BGRAEK/55yEf6hhoKvQ32TWRMBf4SVAAm5jsqXkq6Ha6nnWQW6ph4h9yRb3NPNa8Rfxq/TQR9Hf2xB76LZaDfX59npW+Y8XAaxDHDqgdnyglFSrBQWsUkF8f+5YIHtGQxcPFc X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 15 Apr 2026 08:57:52.6618 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 649a864d-349e-4609-ae12-08de9acd13ff X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[4.158.2.129];Helo=[outbound-uk1.az.dlp.m.darktrace.com] X-MS-Exchange-CrossTenant-AuthSource: DB1PEPF000509F6.eurprd02.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AS8PR08MB7717 On 15/04/2026 09:45, Jie Gan wrote: > > > On 4/15/2026 4:32 PM, Leo Yan wrote: >> On Wed, Apr 15, 2026 at 09:01:09AM +0100, Yeoreum Yun wrote: >> >> [...] >> >>>>> What I am thinking is as SoCs continue to grow more complex with an >>>>> increasing number of subsystems, trace IDs may be exhausted in the >>>>> near >>>>> future. (that's why we have dynamic trace ID allocation/release). >>>> >>>> Thanks for the input. >>>> >>>> I am wandering if we can use "dev->devt" as the trace ID.  A device's >>>> major/minor number is unique in kernel and dev_t is defined as u32: >>>> >>>>    typedef u32 __kernel_dev_t; >>>> >>>> And we can consolidate this for both SYSFS and PERF modes. >>>> >>> >>> When I see the CORESIGHT_TRACE_ID_MAX: >>> >>>   /* architecturally we have 128 IDs some of which are reserved */ >>>    #define CORESIGHT_TRACE_IDS_MAX 128 >>> >>> I think this came from the hardware restriction for number of TRACE_IDs. >>> In this case, clamping the device_id to trace_id seems more complex and >>> reduce some performance perspective. >> >> Sigh, my stupid.  Please ignore my previous comment, let us first fix >> ID leak issue. >> >> Given Jie's comment on the use-out issue, it is valid for me especially >> if a system have many dummy tracers.  We can defer to refactor it >> later (e.g., use separate ranges for hardware and dummy tracers). >> >> thanks for correction! > > Just share some info: > > With my memory, The ARM AMBA ATB Protocol Specification defined a 7-bit > width field for the trace ID, that's where the 128 comes from. (in each > frame, we also have 7-bit field for containing the trace ID) That is true and some IDs in the range (0-128) are reserved. So we actually have less than 128. We need the dynamic allocation, preferrably isolated to a "pool" for the relevant session to make the full use of the space. Suzuki > > Thanks, > Jie >