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X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 27 Jan 2023 06:39:03.6145 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: 5b99eabb-676f-4e40-497b-08db00312e80 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d;Ip=[63.35.35.123];Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM7EUR03FT051.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: DB9PR08MB7724 X-Spam-Status: No, score=-6.7 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,FORGED_SPF_HELO,KAM_DMARC_NONE,NICE_REPLY_A,RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE,TXREP,UNPARSEABLE_RELAY autolearn=no autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 1/27/23 06:30, Joel Brobecker wrote: > Hello, > >>> * [Torbjorn] tdep/29738 >>> Arm M-profile dwarf2 unwinder performance suffers from exponential growth >>> https://sourceware.org/bugzilla/show_bug.cgi?id=29738 >>> >>> patch v3, 2023-01-19, reviewed 2023-01-20: >>> https://sourceware.org/pipermail/gdb-patches/2023-January/195915.html >> >> I just pushed this for master. >> Is it okay to also push the 2 patches to gdb-13-branch? > > For the avoidance of doubt, my understanding is that we are talking > about the following two patches: > > commit d72ba177c85f2ad18d0dcabdd8844532c9acb819 > Author: Torbj�rn SVENSSON > Date: Thu Nov 17 12:17:53 2022 +0100 > Subject: gdb: dwarf2 generic implementation for caching function data > > ... and ... > > commit 5cf11483141a58314834653003e49709b47822d5 > Author: Torbj�rn SVENSSON > Date: Thu Nov 17 12:18:20 2022 +0100 > Subject: gdb/arm: Use new dwarf2 function cache > > I hope I having missed any other patch! > > The first one adds, as the subject indicates, a framework for > caching frame-related information, and the second patch takes > advantage of that framework, > > Luis marked the corresponding PR as "important to fix", so > I'm assuming the impact if we do not backport is significant > (exponentional performance degradation). I was confused into > thinking that this would "only" impact Cortex-m without security > extensions, but maybe it's the opposite actually. It affects m-profiles, but it affects the targets with the security extensions more, as they have more SP registers. > > So the next question is, what is the potential impact if we > backport the patch and there is a bug in it: > > - Well, it touches the generic Arm unwinding code, so > worse case scenario, DWARF-based unwinding is broken? The change is restricted to m-profiles. Unless there is something really off with the caching code, it should break all Arm unwinding. > > - With that said, the patch appears to simply add a cache, > so the logic of it all doesn't appear to be extremely > complicated. So I would rate the risk to be low. That's what it seems to me. I think another round of testing would be a good step to make sure there are no hidden bugs. > > If Tom and/or Simon agree, my assessment is that it is fine > to backport those two patches onto the gdb-13 branch. >