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Wed, 08 Jan 2025 07:41:00 -0800 (PST) MIME-Version: 1.0 References: <48d24318-27d8-4cae-bfdc-64a8828c6f75@arm.com> <87frluw5me.fsf@tromey.com> In-Reply-To: <87frluw5me.fsf@tromey.com> Date: Wed, 8 Jan 2025 23:40:49 +0800 X-Gm-Features: AbW1kvZUEGpYvAO377EVDYUg1GCKoBGSuO7o7222S_HQWPy3LiGdAFSJagvt8Ls Message-ID: Subject: Re: parallel loading of debug info in gdb To: Tom Tromey Cc: Luis Machado , gdb@sourceware.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.30 X-BeenThere: gdb@sourceware.org X-Mailman-Version: 2.1.30 Precedence: list List-Id: Gdb mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: Yubin via Gdb Reply-To: Yubin Errors-To: gdb-bounces~public-inbox=simark.ca@sourceware.org Sender: "Gdb" On Wed, Jan 8, 2025 at 7:45=E2=80=AFAM Tom Tromey wrote: > > Yes dependency is a problem, but some dependent libs are naturally > > independent to be read by parallel. If there could be some way to > > specify this, it would be great. > > If you try git gdb, you can enable background reading with > "maint set dwarf synchronous off". > Thanks, using this command in gdb15.2 indeed make the initial loading faster. > > (There's been at least one request to re-enable this by default for GDB > 16... I wasn't sure if we should, though, considering that the data race > fixes are pretty new.) > > Anyway, background reading is lazier -- the reading is started but gdb > will only pause for it if it is truly needed. > > Note that the library debug info isn't really read in parallel. Or, it > kind of is, depending on how the scheduling shakes out. That is, the > DWARF reader looks at the number of worker threads and splits its work > up accordingly. "Overlap" can only really happen if one such worker > finishes and then the next library's job is scheduled. > > This might be a bad strategy overall. Like, testing on a big machine > showed that the reader didn't parallelize past 8 CPUs, so maybe it would > be better to limit the DWARF reader to 8 tasks. Nobody has worked on > figuring out why it doesn't scale better, though, and I wouldn't want to > change this without knowing more. > > Tom >