task: reuse stack immediately when Task dies and switches to new Task #57496
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Previously we forced it to ping-pong between two stacks, always wasting a little bit of memory (8MB * nthreads) and losing out a bit on possibly warmer caches.
gbaraldi
reviewed
Feb 21, 2025
src/task.c
Outdated
| if (t->ctx.stkbuf == NULL) { | ||
| if (!t->ctx.started && !t->ctx.copy_stack && t->ctx.stkbuf == NULL) { | ||
| // need to allocate the stack | ||
| void *stkbuf = killed && !lastt->ctx.copy_stack && lastt != ptls->root_task && lastt->ctx.bufsz >= t->ctx.bufsz && t->ctx.bufsz <= lastt->ctx.bufsz * 1.5 ? lastt->ctx.stkbuf : NULL; |
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Maybe split this condition in a couple lines, this is a bit hard to read
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I think the size comparison part might not be what's intended? It seems to say t <= lastt && t <= lastt*1.5 but possibly should be t <= lastt && lastt <= t*1.5? (I believe to make sure the reused stack isn't excessively large?)
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Previously we forced it to ping-pong between two stacks, always wasting a little bit of memory (8MB * nthreads) and losing out a bit on possibly warmer caches.