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Lower priority of POSIX_MADV_DONTNEED. (#6671)

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Samuel Williams 2022-11-04 20:13:48 +13:00 committed by GitHub
parent ccf32a5ca4
commit 2bb89b7f11
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Notes: git 2022-11-04 07:14:07 +00:00 
Merged-By: ioquatix <samuel@codeotaku.com>
1 changed files with 18 additions and 3 deletions
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cont.c
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@ -693,21 +693,36 @@ fiber_pool_stack_free(struct fiber_pool_stack * stack)
if (DEBUG) fprintf(stderr, "fiber_pool_stack_free: %p+%"PRIuSIZE" [base=%p, size=%"PRIuSIZE"]\n", base, size, stack->base, stack->size);
#if VM_CHECK_MODE > 0 && defined(MADV_DONTNEED)
// The pages being used by the stack can be returned back to the system.
// That doesn't change the page mapping, but it does allow the system to
// reclaim the physical memory.
// Since we no longer care about the data itself, we don't need to page
// out to disk, since that is costly. Not all systems support that, so
// we try our best to select the most efficient implementation.
// In addition, it's actually slightly desirable to not do anything here,
// but that results in higher memory usage.
#ifdef __wasi__
// WebAssembly doesn't support madvise, so we just don't do anything.
#elif VM_CHECK_MODE > 0 && defined(MADV_DONTNEED)
// This immediately discards the pages and the memory is reset to zero.
madvise(base, size, MADV_DONTNEED);
#elif defined(POSIX_MADV_DONTNEED)
posix_madvise(base, size, POSIX_MADV_DONTNEED);
#elif defined(MADV_FREE_REUSABLE)
// Darwin / macOS / iOS.
// Acknowledge the kernel down to the task info api we make this
// page reusable for future use.
// As for MADV_FREE_REUSE below we ensure in the rare occasions the task was not
// completed at the time of the call to re-iterate.
while (madvise(base, size, MADV_FREE_REUSABLE) == -1 && errno == EAGAIN);
#elif defined(MADV_FREE)
// Recent Linux.
madvise(base, size, MADV_FREE);
#elif defined(MADV_DONTNEED)
// Old Linux.
madvise(base, size, MADV_DONTNEED);
#elif defined(POSIX_MADV_DONTNEED)
// Solaris?
posix_madvise(base, size, POSIX_MADV_DONTNEED);
#elif defined(_WIN32)
VirtualAlloc(base, size, MEM_RESET, PAGE_READWRITE);
// Not available in all versions of Windows.